fix(CallView): light improvement

[DorraJaouad]

☑️ Resolves

• Fix #10567

• When joining a call in group conversation, it is set to grid view even for "connecting" view which makes the tile looks weird. I enforce a speaker view when connecting so to keep a consistent view for all joiners and to avoid having an expanded local video tile.
• Stop following button lost restoring the previous view state because of some watchers enforcing the temporary view (speaker view). I omitted those as startPresentation already handles it.

🖌️ UI Checklist

🖼️ Screenshots / Screencasts

🏚️ Before	🏡 After

🚧 Tasks

• [ ] ...

🏁 Checklist

• [x] 🌏 Tested with Chrome, Firefox and Safari or should not be risky to browser differences
• [ ] 🖥️ Tested with Desktop client or should not be risky for it
• [x] 🖌️ Design was reviewed, approved or inspired by the design team
• [x] ⛑️ Tests are included or not possible
• [x] 📗 User documentation in https://github.com/nextcloud/documentation/tree/master/user_manual/talk has been updated or is not required

[ShGKme]

1. On the call, start following somebody and open stripe
2. Start screensharing from another participant
3. Stop screensharing
4. No you are on the grid view instead of the previous "Following + open stripe"

Is that expected?

Before it returned to the same state, you were before presentation.

[Antreesy]

But I don't see any alternatives.

Hide an option, while there's nothing to place on grid?

[ShGKme]

Not sure it is related, but caught an exception:

TypeError: Cannot read properties of null (reading 'attributes')
    at VueComponent.shouldShowPresenterOverlay

on this line

https://github.com/nextcloud/spreed/blob/79bd33fdcc5de6041f628e699694dd90baf68484/src/components/CallView/CallView.vue#L325

[DorraJaouad]

TypeError: Cannot read properties of null (reading 'attributes') at VueComponent.shouldShowPresenterOverlay

This was unrelated, but fixed as it is involved in "light improvement" :p