Sometimes report_fatal_error is called when there is not a handler function...

Sometimes report_fatal_error is called when there is not a handler function used to fail gracefully. In that case, RunInterruptHandlers is called, which attempts to enter a critical section object. Ensure that the critical section is properly initialized so that this code functions properly, and tools like clang-tidy do not crash in Debug builds.

llvm-svn: 233282