revert r317812 [BasicAA] fix build break by converting the previously introduced assert into an if stmt

The code has a bug, but some tests regress.
I'll discuss this further on the mailing list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317815 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed