Remove unreachable code when thread exits on Linux.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@187995 91177308-0d34-0410-b5e6-96231b3b80d8
Check for division by zero when performing modulus
operations.

<rdar://problem/14656908>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@187996 91177308-0d34-0410-b5e6-96231b3b80d8