Flaky test monkey_business: Cannot read null.pawn

[github-actions]

Flaky tests were detected in this test run. This means that there was a failure that was cleared when the tests were simply restarted.
Failures:

monkey_business: [23:57:23] Runtime in code/datums/proximity_monitor/fields/ai_target_tracking.dm,63: Cannot read null.pawn
proc name: field turf crossed (/datum/proximity_monitor/advanced/ai_target_tracking/field_turf_crossed)
src: /datum/proximity_monitor/advan... (/datum/proximity_monitor/advanced/ai_target_tracking)
call stack:
/datum/proximity_monitor/advan... (/datum/proximity_monitor/advanced/ai_target_tracking): field turf crossed(the rat (/mob/living/basic/mouse/rat), the plating (219,132,8) (/turf/open/floor/plating/dumpsterair), the plating (218,132,8) (/turf/open/floor/plating/dumpsterair))
/datum/proximity_monitor/advan... (/datum/proximity_monitor/advanced/ai_target_tracking): on entered(the plating (218,132,8) (/turf/open/floor/plating/dumpsterair), the rat (/mob/living/basic/mouse/rat), the plating (219,132,8) (/turf/open/floor/plating/dumpsterair), null)
the plating (218,132,8) (/turf/open/floor/plating/dumpsterair):  SendSignal("atom_entered", /list (/list))
the plating (218,132,8) (/turf/open/floor/plating/dumpsterair): Entered(the rat (/mob/living/basic/mouse/rat), the plating (219,132,8) (/turf/open/floor/plating/dumpsterair), null)
the rat (/mob/living/basic/mouse/rat): Move(the plating (218,132,8) (/turf/open/floor/plating/dumpsterair), 8, 0, 1)
the rat (/mob/living/basic/mouse/rat): Move(the plating (218,132,8) (/turf/open/floor/plating/dumpsterair), 8, 0, 1)
the rat (/mob/living/basic/mouse/rat): Move(the plating (218,132,8) (/turf/open/floor/plating/dumpsterair), 8, null)
/datum/idle_behavior/idle_rand... (/datum/idle_behavior/idle_random_walk): perform idle behavior(0.1, /datum/ai_controller/basic_con... (/datum/ai_controller/basic_controller/mouse/rat))
/datum/ai_controller/basic_con... (/datum/ai_controller/basic_controller/mouse/rat): process(0.1)
AI Behavior Ticker (/datum/controller/subsystem/processing/ai_behaviors): fire(1)
AI Behavior Ticker (/datum/controller/subsystem/processing/ai_behaviors): fire(1)
AI Behavior Ticker (/datum/controller/subsystem/processing/ai_behaviors): ignite(1)
Master (/datum/controller/master): RunQueue()
Master (/datum/controller/master): Loop(4)
Master (/datum/controller/master): StartProcessing(0) at code/datums/proximity_monitor/fields/ai_target_tracking.dm:63