fix(NcActions): clear focus trap and move focus only if elements are existing in the DOM

[Antreesy]

☑️ Resolves

• Regression from fix(NcAppSidebar): move focus to sidebar on open and auto return focus on close #5219
• Fix [NcActions] popover is removed before clearForcusTrap #5292
• Also fix issues like Error with displaying the screen demonstration button nextcloud/spreed#9725

There are couple of places, where triggering an action in NcActions (by click, for example) leads to unmounting / breaking re-rendering of NcActions immediately. (Examples in Talk: stop the screensharing (stable28), end the call (main)). In such cases, after nextTick ref elements (popover, menuButton) are no longer present in the DOM (undefined), thus attempt to call methods on them lead to an error (see issues).

Popover has clearFocusTrap in beforeDestroy hook, so changes should be safe to apply (regarding previous PR)

🖼️ Screenshots

No behaviour change, just clean console 🧹

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade

[Antreesy]

/backport to next

[ShGKme]

Do not forget add bug for fixes or enh for new features labels for changelog generation 😛

[Antreesy]

for changelog generation

I thought regression is respected as well, will do in future