Tags: Tag(s) deleted unexpectedly when editing tag name

### Expected

I expect that when I am renaming a tag, I can't accidentally delete it (deleting the tag should be an explicit action).

### Observed

If I choose to edit my tags, remove all the text from a tag name while I'm renaming it, and tap outside that tag's name field, several things happen:

* It deletes the tag.
* If I tap into the field immediately below the tag I was just editing, it deletes that tag, too.
* It leaves a blank tag on any notes using the deleted tag(s).

### Reproduced

1. Create a new note and add a couple tags (e.g. `tag1` and `tag2`).
2. Exit the note editor and open the app drawer.
3. Select "Edit" next to Tags, to edit your tags.
4. Tap into the first tag (e.g. `tag1`) and remove all the text.
5. Tap into the next tag name below it (e.g. `tag2`). Result: Both `tag1` and `tag2` are deleted from the tags list.
6. Open the note again. Notice there is a blank space in the tags editor, and if you tap on it you can remove it like any other tag.

Screencast: https://cloudup.com/cjB0udvL_KT

Make|Model|iOS Version|App Version
-|-|-|-
Apple|iPhone XS|13.5.1|4.23.0.0 beta

Start by reproducing the issue in the Tags editing flow on iOS, following the rename interaction where a tag name is emptied and focus moves to another field. Trace how the edit is committed and how note tags are updated; done means clearing a name cannot implicitly delete tags or leave blank tags on notes.

Written by the indexing model from the issue text.