Impossible to delete any file, when the owner has a numeric name

[salmart-dev]

Describe the bug

Files cannot be deleted when the owner has a numeric name because of the error "wrong owner type".

To Reproduce
Steps to reproduce the behavior:

1. Create a user with name "12345" so that the user Id is "12345"
2. Upload a file that can be viewed in the viewer
3. Open the file with the viewer
4. Attempt deleting the file from the viewer
5. Observe the failure notification

Expected behavior

The file can be deleted