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



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@180235 91177308-0d34-0410-b5e6-96231b3b80d8