* issue 2890: Show a warning icon if media description is missing
* issue 2890: Remove disturbing additional signs
* issue 2890: Add another icon; use a snackbar; change wording; use orange as color
* issue 2890: Remove now unneeded new resource
* issue 2890: Use a toast (also) to avoid elevation problems
* issue 2890: Use snackbar with elevation again; refactor a bit
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