Flaky test check_runtimes: [15:03:25]RUNTIME: Cannot read null.assigned_equipment_preset - code/game/objects/items/devices/radio/headset.dm@379

Flaky tests were detected in [this test run](https://github.com/cmss13-devs/cmss13/actions/runs/28326160981/attempts/1). This means that there was a failure that was cleared when the tests were simply restarted.
Failures:
```
check_runtimes: [15:03:25]RUNTIME: Cannot read null.assigned_equipment_preset - code/game/objects/items/devices/radio/headset.dm@379 at code/defines/../modules/unit_tests/check_runtimes.dm:10
```

Start with code/game/objects/items/devices/radio/headset.dm around line 379 and the check_runtimes test at code/defines/../modules/unit_tests/check_runtimes.dm:10. Review the linked GitHub Actions run and rerun the check to determine why assigned_equipment_preset is read from null; done means the runtime failure no longer occurs intermittently.

Written by the indexing model from the issue text.