Describe the bug
I can mask a service and it creates the /dev/null symlink. But a masked service cannot be unmasked.

To Reproduce
Pick any service and press m to mask it. Press m again and it stays masked.

Expected behavior
A masked service should be unmasked and the /dev/null symlink removed.

Screenshots
None, reproduction is trivial.

Additional context
Tested on a fresh installation of Ubuntu 24.04.