Ensure empty tag names are ignored / thrown out

If we don't already, we should have tests to ensure that a tags line like this:  `@=53;+=ghfd` doesn't result in empty tag names / a tag name that's just the c2c tag prefix. If we don't already, and if tag names must follow a specific structure / set of characters, we can add a test ensuring that too perhaps (either failing or just throwing that tag away, not sure which'd be more appropriate).