Deleting signals sometimes permanently deletes them

[LMayTNG]

Describe the bug
When deleting a signal, it sometimes gets permanently deleted instead of soft deleted.

To Reproduce
Steps to reproduce the behavior:

1. Open an Opossum file
2. Notice the number of signals
3. Click 'Select all' in the signals panel toolbar
4. Click 'Delete'
5. Click 'Show deleted'
6. Notice how the number changed

Expected behavior
The signals should only be soft deleted, and recoverable using 'Show deleted' and 'Restore'

Desktop (please complete the following information):

• OS: Ubuntu