[stdlib] Fix another bug in _getSuperclass
[stdlib] Fix another bug in _getSuperclass

When passed an existential, there is no class object and we should
return nullptr.

Swift SVN r28159

Jnosh/swift,modocache/swift,slavapestov/swift,jckarter/swift,johnno1962d/swift,therealbnut/swift,tjw/swift,cbrentharris/swift,KrishMunot/swift,JaSpa/swift,adrfer/swift,swiftix/swift.old,tjw/swift,danielmartin/swift,khizkhiz/swift,johnno1962d/swift,sschiau/swift,alblue/swift,gregomni/swift,apple/swift,practicalswift/swift,deyton/swift,frootloops/swift,jtbandes/swift,nathawes/swift,return/swift,jtbandes/swift,xedin/swift,natecook1000/swift,aschwaighofer/swift,jopamer/swift,OscarSwanros/swift,glessard/swift,parkera/swift,cbrentharris/swift,lorentey/swift,danielmartin/swift,LeoShimonaka/swift,xwu/swift,mightydeveloper/swift,dduan/swift,Ivacker/swift,kperryua/swift,JGiola/swift,LeoShimonaka/swift,swiftix/swift.old,parkera/swift,brentdax/swift,codestergit/swift,ben-ng/swift,amraboelela/swift,huonw/swift,lorentey/swift,swiftix/swift,JaSpa/swift,gottesmm/swift,LeoShimonaka/swift,jtbandes/swift,JGiola/swift,Ivacker/swift,tkremenek/swift,lorentey/swift,jmgc/swift,tinysun212/swift-windows,gribozavr/swift,manavgabhawala/swift,gmilos/swift,tkremenek/swift,roambotics/swift,parkera/swift,kperryua/swift,allevato/swift,frootloops/swift,atrick/swift,jmgc/swift,dduan/swift,KrishMunot/swift,jtbandes/swift,parkera/swift,SwiftAndroid/swift,stephentyrone/swift,calebd/swift,jmgc/swift,shahmishal/swift,atrick/swift,aschwaighofer/swift,devincoughlin/swift,kstaring/swift,bitjammer/swift,OscarSwanros/swift,natecook1000/swift,codestergit/swift,allevato/swift,ahoppen/swift,gmilos/swift,jopamer/swift,danielmartin/swift,jopamer/swift,OscarSwanros/swift,lorentey/swift,manavgabhawala/swift,dduan/swift,airspeedswift/swift,devincoughlin/swift,alblue/swift,xwu/swift,alblue/swift,shahmishal/swift,practicalswift/swift,stephentyrone/swift,modocache/swift,brentdax/swift,kusl/swift,harlanhaskins/swift,emilstahl/swift,jtbandes/swift,modocache/swift,therealbnut/swift,benlangmuir/swift,gottesmm/swift,LeoShimonaka/swift,aschwaighofer/swift,shahmishal/swift,gottesmm/swift,jckarter/swift,harlanhaskins/swift,adrfer/swift,Ivacker/swift,kentya6/swift,kperryua/swift,JaSpa/swift,jmgc/swift,lorentey/swift,kentya6/swift,shajrawi/swift,felix91gr/swift,amraboelela/swift,tardieu/swift,swiftix/swift.old,kusl/swift,xedin/swift,stephentyrone/swift,practicalswift/swift,MukeshKumarS/Swift,calebd/swift,Ivacker/swift,IngmarStein/swift,slavapestov/swift,stephentyrone/swift,djwbrown/swift,adrfer/swift,LeoShimonaka/swift,tkremenek/swift,kperryua/swift,apple/swift,shajrawi/swift,gregomni/swift,kusl/swift,nathawes/swift,ahoppen/swift,johnno1962d/swift,milseman/swift,uasys/swift,tkremenek/swift,zisko/swift,calebd/swift,tinysun212/swift-windows,johnno1962d/swift,roambotics/swift,devincoughlin/swift,slavapestov/swift,zisko/swift,austinzheng/swift,OscarSwanros/swift,CodaFi/swift,uasys/swift,sschiau/swift,IngmarStein/swift,swiftix/swift,MukeshKumarS/Swift,brentdax/swift,atrick/swift,djwbrown/swift,Ivacker/swift,slavapestov/swift,djwbrown/swift,kstaring/swift,kperryua/swift,swiftix/swift,modocache/swift,mightydeveloper/swift,parkera/swift,arvedviehweger/swift,ken0nek/swift,JaSpa/swift,codestergit/swift,gribozavr/swift,MukeshKumarS/Swift,frootloops/swift,huonw/swift,shajrawi/swift,devincoughlin/swift,alblue/swift,tjw/swift,khizkhiz/swift,russbishop/swift,stephentyrone/swift,sdulal/swift,karwa/swift,tardieu/swift,codestergit/swift,Ivacker/swift,JaSpa/swift,swiftix/swift,stephentyrone/swift,aschwaighofer/swift,sdulal/swift,natecook1000/swift,ben-ng/swift,devincoughlin/swift,KrishMunot/swift,jopamer/swift,shajrawi/swift,JaSpa/swift,ken0nek/swift,arvedviehweger/swift,hughbe/swift,xedin/swift,austinzheng/swift,roambotics/swift,rudkx/swift,tkremenek/swift,kentya6/swift,frootloops/swift,codestergit/swift,codestergit/swift,ben-ng/swift,stephentyrone/swift,uasys/swift,kstaring/swift,MukeshKumarS/Swift,harlanhaskins/swift,calebd/swift,atrick/swift,xedin/swift,benlangmuir/swift,milseman/swift,mightydeveloper/swift,sschiau/swift,jmgc/swift,huonw/swift,xwu/swift,devincoughlin/swift,ken0nek/swift,devincoughlin/swift,ken0nek/swift,milseman/swift,russbishop/swift,atrick/swift,sdulal/swift,gregomni/swift,airspeedswift/swift,harlanhaskins/swift,xedin/swift,huonw/swift,ken0nek/swift,khizkhiz/swift,slavapestov/swift,rudkx/swift,tinysun212/swift-windows,jckarter/swift,JaSpa/swift,natecook1000/swift,amraboelela/swift,benlangmuir/swift,gottesmm/swift,uasys/swift,JGiola/swift,emilstahl/swift,KrishMunot/swift,huonw/swift,karwa/swift,adrfer/swift,ken0nek/swift,karwa/swift,xwu/swift,gribozavr/swift,zisko/swift,shahmishal/swift,jckarter/swift,rudkx/swift,swiftix/swift.old,russbishop/swift,deyton/swift,deyton/swift,kstaring/swift,cbrentharris/swift,sschiau/swift,Jnosh/swift,russbishop/swift,tardieu/swift,IngmarStein/swift,rudkx/swift,xwu/swift,huonw/swift,djwbrown/swift,danielmartin/swift,LeoShimonaka/swift,rudkx/swift,SwiftAndroid/swift,tinysun212/swift-windows,bitjammer/swift,xwu/swift,mightydeveloper/swift,therealbnut/swift,swiftix/swift,amraboelela/swift,khizkhiz/swift,swiftix/swift.old,milseman/swift,ahoppen/swift,nathawes/swift,kperryua/swift,shahmishal/swift,practicalswift/swift,zisko/swift,dduan/swift,apple/swift,bitjammer/swift,kperryua/swift,mightydeveloper/swift,ben-ng/swift,tkremenek/swift,JGiola/swift,IngmarStein/swift,khizkhiz/swift,hughbe/swift,milseman/swift,emilstahl/swift,airspeedswift/swift,gottesmm/swift,benlangmuir/swift,airspeedswift/swift,karwa/swift,ken0nek/swift,frootloops/swift,OscarSwanros/swift,danielmartin/swift,OscarSwanros/swift,sschiau/swift,gmilos/swift,gregomni/swift,JGiola/swift,shahmishal/swift,nathawes/swift,apple/swift,bitjammer/swift,huonw/swift,hooman/swift,tjw/swift,CodaFi/swift,apple/swift,ben-ng/swift,russbishop/swift,gregomni/swift,manavgabhawala/swift,felix91gr/swift,sdulal/swift,russbishop/swift,lorentey/swift,deyton/swift,deyton/swift,aschwaighofer/swift,kstaring/swift,slavapestov/swift,MukeshKumarS/Swift,gmilos/swift,sschiau/swift,benlangmuir/swift,emilstahl/swift,tardieu/swift,gribozavr/swift,tinysun212/swift-windows,kentya6/swift,hooman/swift,danielmartin/swift,SwiftAndroid/swift,khizkhiz/swift,nathawes/swift,gottesmm/swift,practicalswift/swift,ben-ng/swift,CodaFi/swift,glessard/swift,gribozavr/swift,adrfer/swift,xedin/swift,jckarter/swift,kstaring/swift,airspeedswift/swift,tkremenek/swift,KrishMunot/swift,IngmarStein/swift,tardieu/swift,allevato/swift,nathawes/swift,therealbnut/swift,harlanhaskins/swift,felix91gr/swift,kentya6/swift,felix91gr/swift,ben-ng/swift,gmilos/swift,hughbe/swift,glessard/swift,sschiau/swift,modocache/swift,deyton/swift,tinysun212/swift-windows,bitjammer/swift,practicalswift/swift,kentya6/swift,atrick/swift,jckarter/swift,return/swift,IngmarStein/swift,gregomni/swift,hughbe/swift,xedin/swift,hooman/swift,felix91gr/swift,khizkhiz/swift,return/swift,hooman/swift,CodaFi/swift,therealbnut/swift,zisko/swift,hughbe/swift,sdulal/swift,frootloops/swift,gottesmm/swift,gribozavr/swift,roambotics/swift,swiftix/swift,milseman/swift,return/swift,gmilos/swift,glessard/swift,hughbe/swift,glessard/swift,jopamer/swift,mightydeveloper/swift,manavgabhawala/swift,johnno1962d/swift,sdulal/swift,return/swift,emilstahl/swift,manavgabhawala/swift,slavapestov/swift,brentdax/swift,CodaFi/swift,tjw/swift,djwbrown/swift,austinzheng/swift,adrfer/swift,bitjammer/swift,manavgabhawala/swift,johnno1962d/swift,ahoppen/swift,jckarter/swift,adrfer/swift,therealbnut/swift,hughbe/swift,zisko/swift,austinzheng/swift,arvedviehweger/swift,allevato/swift,parkera/swift,jtbandes/swift,airspeedswift/swift,brentdax/swift,danielmartin/swift,MukeshKumarS/Swift,CodaFi/swift,natecook1000/swift,tjw/swift,tardieu/swift,felix91gr/swift,roambotics/swift,amraboelela/swift,SwiftAndroid/swift,emilstahl/swift,shajrawi/swift,tinysun212/swift-windows,johnno1962d/swift,nathawes/swift,return/swift,sdulal/swift,xedin/swift,arvedviehweger/swift,cbrentharris/swift,SwiftAndroid/swift,swiftix/swift.old,dreamsxin/swift,swiftix/swift,OscarSwanros/swift,hooman/swift,glessard/swift,kusl/swift,kusl/swift,karwa/swift,brentdax/swift,allevato/swift,cbrentharris/swift,kusl/swift,manavgabhawala/swift,dduan/swift,hooman/swift,apple/swift,shahmishal/swift,djwbrown/swift,return/swift,dreamsxin/swift,kusl/swift,tardieu/swift,allevato/swift,calebd/swift,practicalswift/swift,karwa/swift,uasys/swift,cbrentharris/swift,KrishMunot/swift,karwa/swift,therealbnut/swift,swiftix/swift.old,LeoShimonaka/swift,Ivacker/swift,ahoppen/swift,alblue/swift,gribozavr/swift,Ivacker/swift,shajrawi/swift,aschwaighofer/swift,cbrentharris/swift,zisko/swift,Jnosh/swift,mightydeveloper/swift,sschiau/swift,amraboelela/swift,frootloops/swift,djwbrown/swift,dduan/swift,parkera/swift,milseman/swift,deyton/swift,allevato/swift,emilstahl/swift,shajrawi/swift,shajrawi/swift,bitjammer/swift,calebd/swift,russbishop/swift,uasys/swift,kstaring/swift,ahoppen/swift,lorentey/swift,austinzheng/swift,arvedviehweger/swift,sdulal/swift,roambotics/swift,devincoughlin/swift,jmgc/swift,harlanhaskins/swift,airspeedswift/swift,hooman/swift,Jnosh/swift,jopamer/swift,lorentey/swift,kentya6/swift,uasys/swift,austinzheng/swift,parkera/swift,natecook1000/swift,SwiftAndroid/swift,arvedviehweger/swift,mightydeveloper/swift,calebd/swift,jtbandes/swift,dduan/swift,aschwaighofer/swift,rudkx/swift,alblue/swift,Jnosh/swift,felix91gr/swift,brentdax/swift,Jnosh/swift,austinzheng/swift,alblue/swift,modocache/swift,codestergit/swift,IngmarStein/swift,shahmishal/swift,MukeshKumarS/Swift,xwu/swift,swiftix/swift.old,SwiftAndroid/swift,amraboelela/swift,modocache/swift,jmgc/swift,emilstahl/swift,CodaFi/swift,cbrentharris/swift,karwa/swift,JGiola/swift,LeoShimonaka/swift,gmilos/swift,kentya6/swift,KrishMunot/swift,tjw/swift,jopamer/swift,Jnosh/swift,arvedviehweger/swift,practicalswift/swift,harlanhaskins/swift,natecook1000/swift,benlangmuir/swift,kusl/swift,gribozavr/swift