Impossible to add back a file after deletion

[murgatt]

Describe the bug
When multiple files have been added to the file list, it is impossible to add back one file after delete it.

To Reproduce
Steps to reproduce the behavior:

1. Start the app and select one file to add
2. In the file list, add another file.
3. Remove this file and try to add it back
4. The file cannot be added

Expected behavior
The file should be added back and appear in the file list.