Orga Media files: edit of file title or folder name leads to error

[MSoeb]

Describe the bug
If a user wants to edit the title of media file or the name of a folder on orga level an error occurs. The edit is not saved. The action is aborted.

Payload:
[
{
"action": "mediafile.update",
"data": [
{
"id": 353,
"title": "asdf2",
"meeting_id": null
}
]
}
]

How to Reproduce
Steps to reproduce the behavior:

1. open Files on orga level
2. upload a file
3. edit the title of the file -> error occurs
4. create a folder
5. edit the title of the folder -> error

Expected behavior
Changing a folder name or a file name should be possible.

[luisa-beerboom]

The problem is twofold:

1. The client sends "meeting_id": null
2. The backend doesn't throw a verbose error

I'll fix the latter in the backend, someone will have to fix the client