toggling 'Important' tag twice doesn't remove "{Remove a, Clear all} tags"

**Describe the bug**
This is by no means anything serious, but a minor QoL issue.

Pressing `Toggle tag "Important"` twice will add & remove said tag which works correctly. However the first press (which adds the tag) also creates `Remove a tag` & `Clear all tags` icons on the toolbar. My understanding is these two buttons should be removed on the second toggle, as the item no longer has any tags.

**To Reproduce**
- create a new entry in copyq by copying something
- open copyq
- press `Toggle tag "Important"`
- note `Remove a tag` & `Clear all tags` icons appear on the UI
- press `Toggle tag "Important"`
- note added icons/buttons do not disappear

**Expected behavior**
`Remove a tag` & `Clear all tags` icons get removed once all tags are removed.

**Repro recording**

https://github.com/user-attachments/assets/226594e5-a60e-40dd-bb86-a935180bd2d0

**Version, OS and Environment**
```
v9.1.0
Qt: 6.7.2
OS: Debian GNU/Linux trixie/sid
DE/DM: i3wm
```