[Driver] Handle null lists in the YAML dependencies file.
[Driver] Handle null lists in the YAML dependencies file.

The right way to do this would be to emit "provides: []", but that's more
work for a format that's ultimately going away. Just accept the null
representation "provides:" for now.

Swift SVN r23394

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