[msan] Fix second parameter in MsanReallocate from previous commit.
[msan] Fix second parameter in MsanReallocate from previous commit.

It's wrong to pass to MsanReallocate a pointer that MSan allocator doesn't own.
Use nullptr instead of ptr to prevent possible (still unlikely) failure.


git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@282390 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt