Fix superadmin is not part of the meeting and tries to add themselves onto the LoS

[Elblinator]

Describe the bug
The superadmin cannot put themselves onto a LoS if they are not a part of the meeting

How to Reproduce
1. Create anything with a LoS (e.g. a topic)
2. Navigate to the LoS
3. Try adding yourself
4. you will get Error in the Console
5. Try adding a poo will trorw a message in the console and create a snackbar Error:

Cannot read properties of null (reading 'id')

The [Error] Message in the console:

TypeError: Cannot read properties of null (reading 'id')
    at _SpeakerControllerService.create (

Expected behavior
What happened before was the the superadmin could put themselves onto the LoS, this behaviour should be recreated

Wanted behavior:
After discussion we've decided that the superadmin have to be part of a meeting to pu themselves on the list of speakers. To assist this behavior, an information message should appear if the superadmin wants to put himself on the list of speakers or wants to create a point of order for himself.

Message: Action not possible. You have to be part of the meeting.

[MSoeb]

Take care: The wanted behavior has changed