Don't crash if we try to interpret the IR (incorrectly in this case) and can't...

Don't crash if we try to interpret the IR (incorrectly in this case) and can't handle the size. This came from trying to do:

(lldb) p typedef float __attribute__((ext_vector_type(8))) __ext_vector_float8; (__ext_vector_float8)$ymm0

llvm-svn: 180235