[MC] - Don't crash on unclosed frame.

llvm-mc can crash when
there is cfi_startproc without cfi_end_proc:

.text
.globl foo
foo:
 .cfi_startproc

Testcase shows the issue, patch fixes it.

Differential revision: https://reviews.llvm.org/D43456

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325564 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed