Flaky test check_runtimes: [11:40:55]RUNTIME: Cannot read null.assigned_equipment_preset - code/game/objects/items/devices/radio/headset.dm@372

Flaky tests were detected in [this test run](https://github.com/cmss13-devs/cmss13/actions/runs/27949838048/attempts/1). This means that there was a failure that was cleared when the tests were simply restarted.
Failures:
```
check_runtimes: [11:40:55]RUNTIME: Cannot read null.assigned_equipment_preset - code/game/objects/items/devices/radio/headset.dm@372 at code/defines/../modules/unit_tests/check_runtimes.dm:10
```

Start with the linked GitHub Actions test run, then inspect check_runtimes.dm at line 10 and code/game/objects/items/devices/radio/headset.dm at line 372. Reproduce the runtime and determine why the flaky check reports null.assigned_equipment_preset; done means the check no longer reports this runtime across reruns.

Written by the indexing model from the issue text.