fix(d.ts): enable angular2 compilation with TS flag --strictNullChecks (#8902)
fix(d.ts): enable angular2 compilation with TS flag --strictNullChecks (#8902)

Eliminate the following compiler error when using TS 1.9+ with strict null checking enabled:

node_modules/@angular/core/src/util/decorators.d.ts(9,5): error TS2411: Property 'extends' of type 'Type | undefined' is not assignable to string index type 'Type | Function | any[]'.

https://github.com/angular/angular/issues/8720
asnowwolf/angular,robwormald/angular,rbevers/angular,mprobst/angular,naomiblack/angular,heathkit/angular,angular-indonesia/angular,mhevery/angular,smartm0use/angular,dtoroshin/n2oDoc,mgechev/angular,tycho01/angular,mzgol/angular,dydek/angular,JanStureNielsen/angular,trshafer/angular,IgorMinar/angular,petebacondarwin/angular,chajath/angular,souvikbasu/angular,templth/angular,angularbrasil/angular,NathanWalker/angular,Brocco/angular,gnomeontherun/angular,chrisse27/angular,kara/angular,gjungb/angular,tycho01/angular,vicb/angular,juleskremer/angular,tbosch/angular,smartm0use/angular,chajath/angular,robwormald/angular,smartm0use/angular,ScottSWu/angular,tolemac/angular,xcaliber-tech/angular,awerlang/angular,gionkunz/angular,chalin/angular,alexeagle/angular,snaptech/angular,chalin/angular,SaltyDH/angular,laskoviymishka/angular,mgechev/angular,chalin/angular,blesh/angular,kylecordes/angular,rkirov/angular,vsavkin/angular,cexbrayat/angular,cironunes/angular,rkirov/angular,robwormald/angular,alxhub/angular,ValtoFrameworks/Angular-2,xcaliber-tech/angular,juristr/angular,youdz/angular,cassand/angular,graveto/angular,juristr/angular,rjamet/angular,vinagreti/angular,alxhub/angular,ocombe/angular,mdegoo/angular,laco0416/angular,mlaval/angular,souvikbasu/angular,NathanWalker/angular,mzgol/angular,royling/angular,hansl/angular,kylecordes/angular,kylecordes/angular,xcaliber-tech/angular,pkozlowski-opensource/angular,juleskremer/angular,Toxicable/angular,gkalpak/angular,alexeagle/angular,alfonso-presa/angular,chuckjaz/angular,manekinekko/angular,cironunes/angular,heathkit/angular,petebacondarwin/angular,ScottSWu/angular,JiaLiPassion/angular,mzgol/angular,alexeagle/angular,dsebastien/angular,dydek/angular,e-hein/angular,juristr/angular,mprobst/angular,blesh/angular,sjtrimble/angular,robwormald/angular,AlmogShaul/angular,vsavkin/angular,domusofsail/angular,naomiblack/angular,e-hein/angular,zhura/angular,pkozlowski-opensource/angular,JSMike/angular,angularbrasil/angular,zhura/angular,laco0416/angular,dejour/angular,LucasSloan/angular,gionkunz/angular,aboveyou00/angular,hterkelsen/angular,souvikbasu/angular,ScottSWu/angular,mlaval/angular,mikeybyker/angular,pk-karthik/framework-js-angular,Flounn/angular,pkozlowski-opensource/angular,vikerman/angular,LucasSloan/angular,petebacondarwin/angular,wKoza/angular,cexbrayat/angular,rjamet/angular,ScottSWu/angular,juristr/angular,zhura/angular,templth/angular,nosovk/angular,alamgird/angular,aboveyou00/angular,alfonso-presa/angular,brandonroberts/angular,alamgird/angular,kwalrath/angular,Brocco/angular,gdi2290/angular,laskoviymishka/angular,cironunes/angular,dtoroshin/n2oDoc,chajath/angular,juristr/angular,trshafer/angular,SaltyDH/angular,IgorMinar/angular,ghetolay/angular,Brocco/angular,cassand/angular,brandonroberts/angular,laskoviymishka/angular,naomiblack/angular,robwormald/angular,angular/angular,manekinekko/angular,xcaliber-tech/angular,matsko/angular,templth/angular,gkalpak/angular,Toxicable/angular,aboveyou00/angular,dsebastien/angular,cexbrayat/angular,JanStureNielsen/angular,ollie314/angular,vicb/angular,hterkelsen/angular,angularbrasil/angular,ocombe/angular,itamark/angular,itamark/angular,filipesilva/angular,xcaliber-tech/angular,asnowwolf/angular,tbosch/angular,mprobst/angular,diestrin/angular,Flounn/angular,zhura/angular,UIUXEngineering-Forks/angular,kylecordes/angular,youdz/angular,IdeaBlade/angular,ScottSWu/angular,royling/angular,hansl/angular,diestrin/angular,IgorMinar/angular,meeroslav/angular,tycho01/angular,SekibOmazic/angular,ocombe/angular,youdz/angular,manekinekko/angular,asnowwolf/angular,hansl/angular,SekibOmazic/angular,dtoroshin/n2oDoc,UIUXEngineering-Forks/angular,StephenFluin/angular,e-hein/angular,tolemac/angular,Flounn/angular,snaptech/angular,cironunes/angular,UIUXEngineering-Forks/angular,shairez/angular,tolemac/angular,StephenFluin/angular,kylecordes/angular,LucasSloan/angular,souvikbasu/angular,kegluneq/angular,juristr/angular,UIUXEngineering-Forks/angular,alexeagle/angular,ocombe/angular,graveto/angular,angularbrasil/angular,rjamet/angular,diestrin/angular,templth/angular,alexeagle/angular,ultrasonicsoft/angular,mlaval/angular,chuckjaz/angular,gkalpak/angular,cexbrayat/angular,pkozlowski-opensource/angular,gdi2290/angular,Mathou54/angular,alamgird/angular,petebacondarwin/angular,petebacondarwin/angular,pk-karthik/framework-js-angular,IgorMinar/angular,alexeagle/angular,angular-indonesia/angular,gionkunz/angular,jonrimmer/angular,JSMike/angular,gnomeontherun/angular,shairez/angular,ValtoFrameworks/Angular-2,sarunint/angular,pk-karthik/framework-js-angular,JiaLiPassion/angular,tolemac/angular,gdi2290/angular,jesperronn/angular,Flounn/angular,smartm0use/angular,trshafer/angular,dsebastien/angular,SekibOmazic/angular,alfonso-presa/angular,gjungb/angular,mgechev/angular,pk-karthik/framework-js-angular,sjtrimble/angular,blesh/angular,graveto/angular,alfonso-presa/angular,vicb/angular,StephenFluin/angular,StephenFluin/angular,gdi2290/angular,meeroslav/angular,juleskremer/angular,mdegoo/angular,SekibOmazic/angular,aboveyou00/angular,brandonroberts/angular,laco0416/angular,vikerman/angular,angular-indonesia/angular,snaptech/angular,chuckjaz/angular,JanStureNielsen/angular,zhura/angular,mgiambalvo/angular,laco0416/angular,mhevery/angular,jasonaden/angular,rbevers/angular,sarunint/angular,hansl/angular,Toxicable/angular,not-for-me/angular,ValtoFrameworks/Angular-2,tycho01/angular,sarunint/angular,gdi2290/angular,templth/angular,cexbrayat/angular,vamsivarikuti/angular,UIUXEngineering/angular,snaptech/angular,angular/angular,mgol/angular,JanStureNielsen/angular,Brocco/angular,dsebastien/angular,ocombe/angular,Mathou54/angular,vicb/angular,wKoza/angular,Mathou54/angular,vandres/angular,ghetolay/angular,cassand/angular,shairez/angular,nosovk/angular,wKoza/angular,Toxicable/angular,ultrasonicsoft/angular,robwormald/angular,kara/angular,wKoza/angular,mikeybyker/angular,vsavkin/angular,youdz/angular,royling/angular,ollie314/angular,angular-indonesia/angular,angularbrasil/angular,meeroslav/angular,hterkelsen/angular,itamark/angular,ollie314/angular,meeroslav/angular,alxhub/angular,aboveyou00/angular,dejour/angular,snaptech/angular,vandres/angular,royling/angular,SekibOmazic/angular,IgorMinar/angular,kara/angular,alfonso-presa/angular,mgechev/angular,laco0416/angular,ghetolay/angular,gjungb/angular,JSMike/angular,mgol/angular,rkirov/angular,mgol/angular,kwalrath/angular,vinagreti/angular,dydek/angular,royling/angular,shairez/angular,naomiblack/angular,Toxicable/angular,vandres/angular,mdegoo/angular,SekibOmazic/angular,blesh/angular,domusofsail/angular,hansl/angular,gjungb/angular,matsko/angular,sjtrimble/angular,dejour/angular,hterkelsen/angular,tycho01/angular,filipesilva/angular,jesperronn/angular,chrisse27/angular,jasonaden/angular,gkalpak/angular,shairez/angular,vinagreti/angular,laco0416/angular,laskoviymishka/angular,rbevers/angular,vikerman/angular,chuckjaz/angular,alfonso-presa/angular,jonrimmer/angular,kara/angular,kegluneq/angular,ValtoFrameworks/Angular-2,JSMike/angular,kwalrath/angular,NathanWalker/angular,angular/angular,mgiambalvo/angular,dydek/angular,NathanWalker/angular,gjungb/angular,smartm0use/angular,kegluneq/angular,dejour/angular,trshafer/angular,mikeybyker/angular,IdeaBlade/angular,alxhub/angular,panuruj/angular,kwalrath/angular,vamsivarikuti/angular,laskoviymishka/angular,dtoroshin/n2oDoc,not-for-me/angular,mdegoo/angular,JiaLiPassion/angular,alamgird/angular,tbosch/angular,mzgol/angular,gionkunz/angular,sarunint/angular,mhevery/angular,zhura/angular,heathkit/angular,ScottSWu/angular,cironunes/angular,vamsivarikuti/angular,vikerman/angular,blesh/angular,chalin/angular,kegluneq/angular,youdz/angular,vsavkin/angular,jonrimmer/angular,pkozlowski-opensource/angular,StephenFluin/angular,alxhub/angular,mzgol/angular,dsebastien/angular,angularbrasil/angular,UIUXEngineering/angular,mgiambalvo/angular,awerlang/angular,chrisse27/angular,mgiambalvo/angular,rjamet/angular,AlmogShaul/angular,mhevery/angular,graveto/angular,chajath/angular,ultrasonicsoft/angular,cassand/angular,asnowwolf/angular,petebacondarwin/angular,vicb/angular,rkirov/angular,manekinekko/angular,mgol/angular,brandonroberts/angular,tbosch/angular,filipesilva/angular,hterkelsen/angular,graveto/angular,nosovk/angular,juleskremer/angular,mgol/angular,angular/angular,filipesilva/angular,chuckjaz/angular,JanStureNielsen/angular,jesperronn/angular,JSMike/angular,awerlang/angular,domusofsail/angular,cassand/angular,ollie314/angular,vsavkin/angular,dydek/angular,jasonaden/angular,IdeaBlade/angular,jesperronn/angular,SaltyDH/angular,meeroslav/angular,Brocco/angular,vikerman/angular,Mathou54/angular,tbosch/angular,UIUXEngineering/angular,SaltyDH/angular,cassand/angular,mhevery/angular,ValtoFrameworks/Angular-2,wKoza/angular,diestrin/angular,hansl/angular,NathanWalker/angular,gionkunz/angular,vamsivarikuti/angular,not-for-me/angular,aboveyou00/angular,mgechev/angular,graveto/angular,mgol/angular,rkirov/angular,mlaval/angular,tolemac/angular,youdz/angular,wKoza/angular,domusofsail/angular,JiaLiPassion/angular,mhevery/angular,e-hein/angular,vicb/angular,jonrimmer/angular,chrisse27/angular,NathanWalker/angular,vinagreti/angular,mgiambalvo/angular,jesperronn/angular,mzgol/angular,panuruj/angular,panuruj/angular,IgorMinar/angular,UIUXEngineering-Forks/angular,itamark/angular,nosovk/angular,SaltyDH/angular,awerlang/angular,trshafer/angular,heathkit/angular,mdegoo/angular,jonrimmer/angular,domusofsail/angular,rkirov/angular,kegluneq/angular,brandonroberts/angular,gnomeontherun/angular,kwalrath/angular,dejour/angular,AlmogShaul/angular,Mathou54/angular,sarunint/angular,matsko/angular,ghetolay/angular,ghetolay/angular,sjtrimble/angular,vamsivarikuti/angular,jasonaden/angular,rbevers/angular,kegluneq/angular,vinagreti/angular,naomiblack/angular,hterkelsen/angular,ocombe/angular,matsko/angular,nosovk/angular,e-hein/angular,rbevers/angular,mikeybyker/angular,UIUXEngineering/angular,filipesilva/angular,snaptech/angula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