fix(language-service): guard access to `Symbol.members` (#15529)
fix(language-service): guard access to `Symbol.members` (#15529)

Fixes #15528 

What is the current behavior?
The language service access TypeScript's Symbol.members without checking for null or undefined.
What is the new behavior?
The access is guarded.
angular-indonesia/angular,kara/angular,Toxicable/angular,blesh/angular,alxhub/angular,mgol/angular,aboveyou00/angular,jonrimmer/angular,vikerman/angular,juristr/angular,sarunint/angular,vamsivarikuti/angular,Brocco/angular,rjamet/angular,heathkit/angular,vamsivarikuti/angular,ultrasonicsoft/angular,chrisse27/angular,mprobst/angular,petebacondarwin/angular,mhevery/angular,filipesilva/angular,mlaval/angular,vicb/angular,jonrimmer/angular,kegluneq/angular,chuckjaz/angular,StephenFluin/angular,mdegoo/angular,meeroslav/angular,juristr/angular,hansl/angular,juleskremer/angular,snaptech/angular,Toxicable/angular,ocombe/angular,juristr/angular,mlaval/angular,petebacondarwin/angular,juleskremer/angular,kara/angular,angular-indonesia/angular,jonrimmer/angular,angular-indonesia/angular,matsko/angular,aboveyou00/angular,filipesilva/angular,LucasSloan/angular,mgol/angular,mhevery/angular,vsavkin/angular,chrisse27/angular,brandonroberts/angular,ValtoFrameworks/Angular-2,vicb/angular,hansl/angular,heathkit/angular,wKoza/angular,vikerman/angular,petebacondarwin/angular,mgol/angular,LucasSloan/angular,ghetolay/angular,petebacondarwin/angular,sarunint/angular,matsko/angular,dsebastien/angular,diestrin/angular,IgorMinar/angular,Brocco/angular,dsebastien/angular,ghetolay/angular,royling/angular,mgechev/angular,brandonroberts/angular,sarunint/angular,mgol/angular,kwalrath/angular,alexeagle/angular,alxhub/angular,wKoza/angular,JiaLiPassion/angular,ultrasonicsoft/angular,mlaval/angular,IdeaBlade/angular,angular/angular,gnomeontherun/angular,pkozlowski-opensource/angular,ultrasonicsoft/angular,mprobst/angular,souvikbasu/angular,dtoroshin/n2oDoc,mhevery/angular,mlaval/angular,Brocco/angular,angular-indonesia/angular,brandonroberts/angular,NathanWalker/angular,IdeaBlade/angular,ValtoFrameworks/Angular-2,kegluneq/angular,rjamet/angular,cironunes/angular,kara/angular,jonrimmer/angular,nosovk/angular,angular/angular,cironunes/angular,wKoza/angular,chuckjaz/angular,LucasSloan/angular,NathanWalker/angular,StephenFluin/angular,trshafer/angular,kegluneq/angular,gjungb/angular,pkozlowski-opensource/angular,robwormald/angular,ghetolay/angular,vsavkin/angular,dtoroshin/n2oDoc,trshafer/angular,mgiambalvo/angular,nosovk/angular,robwormald/angular,gkalpak/angular,StephenFluin/angular,kegluneq/angular,sarunint/angular,manekinekko/angular,shairez/angular,mdegoo/angular,nosovk/angular,kara/angular,angular/angular,ocombe/angular,gdi2290/angular,diestrin/angular,mgiambalvo/angular,mdegoo/angular,ghetolay/angular,mzgol/angular,jasonaden/angular,meeroslav/angular,mzgol/angular,chrisse27/angular,mgechev/angular,pk-karthik/framework-js-angular,ocombe/angular,vicb/angular,chalin/angular,matsko/angular,kara/angular,heathkit/angular,alxhub/angular,cexbrayat/angular,matsko/angular,vikerman/angular,hansl/angular,royling/angular,juleskremer/angular,tbosch/angular,aboveyou00/angular,kwalrath/angular,ValtoFrameworks/Angular-2,manekinekko/angular,souvikbasu/angular,Brocco/angular,blesh/angular,meeroslav/angular,gnomeontherun/angular,hansl/angular,petebacondarwin/angular,juristr/angular,filipesilva/angular,robwormald/angular,brandonroberts/angular,mdegoo/angular,juleskremer/angular,rkirov/angular,shairez/angular,mgiambalvo/angular,alexeagle/angular,vsavkin/angular,angularbrasil/angular,gnomeontherun/angular,vsavkin/angular,filipesilva/angular,ocombe/angular,mprobst/angular,dtoroshin/n2oDoc,petebacondarwin/angular,IgorMinar/angular,nosovk/angular,vamsivarikuti/angular,cexbrayat/angular,ultrasonicsoft/angular,pkozlowski-opensource/angular,royling/angular,rkirov/angular,blesh/angular,LucasSloan/angular,jonrimmer/angular,gdi2290/angular,trshafer/angular,JiaLiPassion/angular,manekinekko/angular,gjungb/angular,wKoza/angular,IgorMinar/angular,souvikbasu/angular,snaptech/angular,filipesilva/angular,rkirov/angular,pk-karthik/framework-js-angular,mgol/angular,kwalrath/angular,tbosch/angular,StephenFluin/angular,mlaval/angular,angularbrasil/angular,tbosch/angular,gnomeontherun/angular,trshafer/angular,gkalpak/angular,gdi2290/angular,cironunes/angular,jasonaden/angular,manekinekko/angular,NathanWalker/angular,kwalrath/angular,sarunint/angular,IdeaBlade/angular,Toxicable/angular,ocombe/angular,aboveyou00/angular,rkirov/angular,juristr/angular,shairez/angular,Toxicable/angular,heathkit/angular,ultrasonicsoft/angular,cexbrayat/angular,dsebastien/angular,diestrin/angular,NathanWalker/angular,royling/angular,mdegoo/angular,shairez/angular,gdi2290/angular,mdegoo/angular,chrisse27/angular,mhevery/angular,gdi2290/angular,trshafer/angular,dsebastien/angular,pkozlowski-opensource/angular,rjamet/angular,mprobst/angular,NathanWalker/angular,blesh/angular,cironunes/angular,juristr/angular,LucasSloan/angular,mgechev/angular,pk-karthik/framework-js-angular,dsebastien/angular,alxhub/angular,JiaLiPassion/angular,aboveyou00/angular,kwalrath/angular,ValtoFrameworks/Angular-2,ValtoFrameworks/Angular-2,gkalpak/angular,meeroslav/angular,IdeaBlade/angular,smartm0use/angular,meeroslav/angular,IgorMinar/angular,robwormald/angular,gjungb/angular,gjungb/angular,chalin/angular,chalin/angular,juleskremer/angular,ghetolay/angular,vsavkin/angular,dtoroshin/n2oDoc,LucasSloan/angular,kegluneq/angular,snaptech/angular,vamsivarikuti/angular,hansl/angular,trshafer/angular,dsebastien/angular,heathkit/angular,brandonroberts/angular,vikerman/angular,souvikbasu/angular,Brocco/angular,Brocco/angular,wKoza/angular,chuckjaz/angular,chrisse27/angular,alexeagle/angular,cexbrayat/angular,manekinekko/angular,royling/angular,chuckjaz/angular,vikerman/angular,StephenFluin/angular,mhevery/angular,smartm0use/angular,pkozlowski-opensource/angular,JiaLiPassion/angular,mzgol/angular,wKoza/angular,mgiambalvo/angular,rkirov/angular,blesh/angular,IdeaBlade/angular,angularbrasil/angular,snaptech/angular,aboveyou00/angular,chuckjaz/angular,tbosch/angular,gdi2290/angular,angularbrasil/angular,jasonaden/angular,alexeagle/angular,chuckjaz/angular,jasonaden/angular,gjungb/angular,shairez/angular,matsko/angular,hansl/angular,rkirov/angular,vamsivarikuti/angular,IgorMinar/angular,brandonroberts/angular,mgol/angular,ocombe/angular,cironunes/angular,sarunint/angular,pk-karthik/framework-js-angular,mgechev/angular,cironunes/angular,jasonaden/angular,snaptech/angular,mzgol/angular,mgiambalvo/angular,alexeagle/angular,snaptech/angular,NathanWalker/angular,mprobst/angular,vicb/angular,cexbrayat/angular,chalin/angular,kara/angular,rjamet/angular,ultrasonicsoft/angular,jasonaden/angular,angularbrasil/angular,jonrimmer/angular,tbosch/angular,kegluneq/angular,mprobst/angular,alexeagle/angular,vicb/angular,smartm0use/angular,souvikbasu/angular,gkalpak/angular,mzgol/angular,Toxicable/angular,mhevery/angular,mgechev/angular,angular/angular,alxhub/angular,diestrin/angular,robwormald/angular,smartm0use/angular,robwormald/angular,heathkit/angular,angularbrasil/angular,dtoroshin/n2oDoc,vicb/angular,vikerman/angular,IgorMinar/angular,mzgol/angular,nosovk/angular,smartm0use/angular,pk-karthik/framework-js-angular,manekinekko/angular,Toxicable/angular