Appcompatcache parser: Issue with -c and broken shimcache

Ran into an edge case that causes appcompatcacheparser to die rather than safely error out

Had a shimcache value that was empty but had about 48 bytes of 00's. Once the tool found the key it died.

Also if you run -c with a value,X, it just attempts to look for ControlSet00X and then dies. So there's no validation that that would be a valid value and safely closing.