Print an error message if no definitions are specified.
Explicitly point at that no definitions are deleted if there's a problem.
Delete all definitions if '*' is the only thing given.
The check commands failed to catch errors after the DefinitionExpressions have been converted into Definitions, espeically leading reference cycles. Not they do catch them. This is a quick, stop-gap fix; the error checkers really need to be cleaned up.
Check for errors in the other commands.
Fix the test.