When removing a tag from all models, a blank filter remains on reload

[Aevaris]

Describe the bug
After removing a tag from all models, that tag is still in the URL and blank on the filter panel.

To Reproduce
Steps to reproduce the behavior:

1. Click a tag
2. Select all models and remove that tag

Expected behavior
Clear from the URL and from the GUI to save the user clicks

Screenshots

[Floppy]

This happens because the tag will have been completely removed, but the filter list doesn't check that the tag exists before applying it. So, we should make it check. Thanks for spotting it!