[Sema] Don't crash in matchCallArguments if autoclosure type is not a function type
[Sema] Don't crash in matchCallArguments if autoclosure type is not a function type

During code completion, the function type may be a placeholder type. Don't crash in those cases.

apple/swift,atrick/swift,atrick/swift,benlangmuir/swift,roambotics/swift,benlangmuir/swift,gregomni/swift,JGiola/swift,roambotics/swift,ahoppen/swift,JGiola/swift,benlangmuir/swift,roambotics/swift,glessard/swift,gregomni/swift,ahoppen/swift,benlangmuir/swift,gregomni/swift,apple/swift,glessard/swift,ahoppen/swift,glessard/swift,apple/swift,roambotics/swift,benlangmuir/swift,benlangmuir/swift,glessard/swift,glessard/swift,roambotics/swift,gregomni/swift,atrick/swift,atrick/swift,apple/swift,apple/swift,ahoppen/swift,JGiola/swift,gregomni/swift,JGiola/swift,atrick/swift,JGiola/swift,gregomni/swift,ahoppen/swift,apple/swift,roambotics/swift,glessard/swift,JGiola/swift,ahoppen/swift,atrick/swift