no issue names are considered invalid when using `issue_pattern`

using `+abcdefg.feature` fails when using `issue_pattern` 
```
Error: Issue name '' does not match the configured pattern, '[A-Z]+-\d+'
```
I think it's okay to ignore these when checking for the pattern - wdyt? Maybe in the future we can add a flag to require a name and prevent non-issues (beyond my needs & scope for now)