When adding a non-existent file or directory via the web UI to mediatomb, I get no error message. The ajax response should include one.
Steps to reproduce:
1. log into web ui
2. on the top left, click "Filesystem"
3. navigate to some folder
4. on the right, all files in that folder appear with a "+" on the right to add them to mediatomb
5. on the file system, move the file away
6. click the "+" for the file in the web ui
7. no error message is issued.
Inspecting the ajax response shows no error message.