Fix compilation: don't convert NULL to a pointer-incompatible type.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200536 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Run LSan for ASan unit tests only on 64-bit Linux

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@200537 91177308-0d34-0410-b5e6-96231b3b80d8