[MachineVerifier] Avoid reference to nullptr

Instantiation of the MachineVerifierPass through
PassInfo::getNormalCtor would yield a segfault since the default
constructor of the MachineVerifierPass takes a reference to nullptr.

Patch by Simone Pellegrini.

Differential Revision: https://reviews.llvm.org/D31387



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298987 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed