Disallow Empty Exclusion Sets

[bchintx]

Could we consider disallowing empty Exclusion Set entries from being created? Since there's already a fixed "Don't Exclude Files" menu item in the Exclusion Set dropdown list, empty set entries are redundant. Plus, they look odd in the dropdown menu.

Steps to reproduce:

1. launch Brackets and open any project
2. + + F to display the Find in Project bar
3. Click the Exclusion Set dropdown button.
4. Click "New Exclusion Set..."
5. in the resulting dialog, just click OK without entering any exclusions or name.
6. Click the Exclusion Set dropdown button again.

Observed:
blank line in the dropdown menu

Expected:
perhaps consider not allowing the empty set to be created by the Edit Exclusion Set dialog? maybe disable the OK button or just don't create anything if they click OK?

[bchintx]

Found while testing the feature on Windows in Pull Request #7836.

@njx @RaymondLim IMHO, this is probably low priority since it's mostly cosmetic.

[RaymondLim]

We may have to disable the OK button since we also need to take care of editing an existing exclusion set where we can't silently dismiss the dialog when the user empty the filter set.

[RaymondLim]

FBNC to @bchintx

[bchintx]

Works great! Thanks! @RaymondLim and @SAplayer