AST: Fix potential null dereference in SubstitutionMap::lookupConformance()
AST: Fix potential null dereference in SubstitutionMap::lookupConformance()

If there's no lazy resolver and we're looking at an incomplete conformance,
fail with an error instead of crashing. The caller will likely crash also,
but at least this allows better recovery in this case in the future.

shahmishal/swift,rudkx/swift,amraboelela/swift,xedin/swift,harlanhaskins/swift,apple/swift,stephentyrone/swift,huonw/swift,tjw/swift,huonw/swift,glessard/swift,practicalswift/swift,zisko/swift,shahmishal/swift,brentdax/swift,brentdax/swift,atrick/swift,frootloops/swift,glessard/swift,roambotics/swift,amraboelela/swift,OscarSwanros/swift,benlangmuir/swift,benlangmuir/swift,swiftix/swift,amraboelela/swift,devincoughlin/swift,gregomni/swift,aschwaighofer/swift,practicalswift/swift,xwu/swift,parkera/swift,stephentyrone/swift,devincoughlin/swift,hooman/swift,austinzheng/swift,amraboelela/swift,OscarSwanros/swift,nathawes/swift,devincoughlin/swift,airspeedswift/swift,natecook1000/swift,roambotics/swift,rudkx/swift,devincoughlin/swift,jckarter/swift,nathawes/swift,karwa/swift,alblue/swift,nathawes/swift,swiftix/swift,atrick/swift,shajrawi/swift,nathawes/swift,rudkx/swift,huonw/swift,jckarter/swift,stephentyrone/swift,shajrawi/swift,CodaFi/swift,tkremenek/swift,sschiau/swift,frootloops/swift,shahmishal/swift,stephentyrone/swift,shahmishal/swift,harlanhaskins/swift,lorentey/swift,hooman/swift,airspeedswift/swift,alblue/swift,frootloops/swift,shajrawi/swift,apple/swift,jckarter/swift,devincoughlin/swift,atrick/swift,nathawes/swift,austinzheng/swift,parkera/swift,alblue/swift,allevato/swift,ahoppen/swift,karwa/swift,JGiola/swift,harlanhaskins/swift,karwa/swift,parkera/swift,zisko/swift,austinzheng/swift,swiftix/swift,sschiau/swift,sschiau/swift,harlanhaskins/swift,gregomni/swift,devincoughlin/swift,jmgc/swift,gregomni/swift,jmgc/swift,tjw/swift,ahoppen/swift,gregomni/swift,CodaFi/swift,uasys/swift,ahoppen/swift,rudkx/swift,ahoppen/swift,jopamer/swift,hooman/swift,danielmartin/swift,aschwaighofer/swift,tjw/swift,aschwaighofer/swift,xwu/swift,amraboelela/swift,xedin/swift,brentdax/swift,natecook1000/swift,tkremenek/swift,brentdax/swift,tjw/swift,atrick/swift,jopamer/swift,shajrawi/swift,gregomni/swift,gribozavr/swift,practicalswift/swift,natecook1000/swift,lorentey/swift,allevato/swift,jopamer/swift,xedin/swift,hooman/swift,frootloops/swift,jmgc/swift,JGiola/swift,practicalswift/swift,allevato/swift,jopamer/swift,harlanhaskins/swift,gribozavr/swift,JGiola/swift,uasys/swift,practicalswift/swift,rudkx/swift,natecook1000/swift,danielmartin/swift,glessard/swift,devincoughlin/swift,alblue/swift,natecook1000/swift,shajrawi/swift,jmgc/swift,jckarter/swift,tkremenek/swift,jopamer/swift,karwa/swift,benlangmuir/swift,amraboelela/swift,OscarSwanros/swift,sschiau/swift,lorentey/swift,benlangmuir/swift,jopamer/swift,ahoppen/swift,CodaFi/swift,huonw/swift,shajrawi/swift,sschiau/swift,ahoppen/swift,glessard/swift,austinzheng/swift,practicalswift/swift,uasys/swift,benlangmuir/swift,zisko/swift,hooman/swift,huonw/swift,tjw/swift,zisko/swift,jmgc/swift,shahmishal/swift,sschiau/swift,parkera/swift,karwa/swift,xedin/swift,harlanhaskins/swift,lorentey/swift,parkera/swift,karwa/swift,jckarter/swift,harlanhaskins/swift,natecook1000/swift,swiftix/swift,airspeedswift/swift,amraboelela/swift,apple/swift,shajrawi/swift,uasys/swift,allevato/swift,frootloops/swift,xwu/swift,jckarter/swift,brentdax/swift,OscarSwanros/swift,roambotics/swift,benlangmuir/swift,JGiola/swift,huonw/swift,gribozavr/swift,austinzheng/swift,JGiola/swift,lorentey/swift,airspeedswift/swift,allevato/swift,xwu/swift,aschwaighofer/swift,roambotics/swift,danielmartin/swift,OscarSwanros/swift,hooman/swift,gribozavr/swift,tkremenek/swift,danielmartin/swift,danielmartin/swift,jopamer/swift,alblue/swift,rudkx/swift,frootloops/swift,lorentey/swift,alblue/swift,allevato/swift,CodaFi/swift,CodaFi/swift,aschwaighofer/swift,OscarSwanros/swift,hooman/swift,JGiola/swift,austinzheng/swift,jmgc/swift,gribozavr/swift,brentdax/swift,practicalswift/swift,karwa/swift,shahmishal/swift,airspeedswift/swift,zisko/swift,tkremenek/swift,gregomni/swift,shajrawi/swift,lorentey/swift,lorentey/swift,parkera/swift,CodaFi/swift,roambotics/swift,zisko/swift,practicalswift/swift,jmgc/swift,atrick/swift,xedin/swift,apple/swift,uasys/swift,xwu/swift,OscarSwanros/swift,nathawes/swift,swiftix/swift,glessard/swift,shahmishal/swift,jckarter/swift,uasys/swift,atrick/swift,karwa/swift,apple/swift,xwu/swift,tjw/swift,devincoughlin/swift,stephentyrone/swift,danielmartin/swift,brentdax/swift,gribozavr/swift,aschwaighofer/swift,natecook1000/swift,gribozavr/swift,airspeedswift/swift,tkremenek/swift,parkera/swift,nathawes/swift,alblue/swift,uasys/swift,swiftix/swift,swiftix/swift,tkremenek/swift,roambotics/swift,xedin/swift,aschwaighofer/swift,frootloops/swift,stephentyrone/swift,xedin/swift,huonw/swift,allevato/swift,airspeedswift/swift,danielmartin/swift,sschiau/swift,tjw/swift,glessard/swift,zisko/swift,austinzheng/swift,gribozavr/swift,CodaFi/swift,xwu/swift,xedin/swift,stephentyrone/swift,shahmishal/swift,parkera/swift,sschiau/swift,apple/swift