[BasicAA] fix build break by converting the previously introduced assert into an if stmt
Apparently V1Size == -1 doest imply V2Size == -1, which is a bit surprising to me.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317812 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed