This is made possible by removing an assert in llc that assumed
MIRParser::parseLLVMModule would exit on error. MIRParser's documentation states
that it returns null if a parsing error occurs, so there's no reason to assert.
We can instead just fall through to where the check for a module is performed
and exit if it is null.
This commit is part of the clean-up after r269655.
Fixes PR27770
Differential Revision: http://reviews.llvm.org/D20371
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272254 91177308-0d34-0410-b5e6-96231b3b80d8