Flaky test failure with no obvious source

[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:

[LikeLakers2]

The test failure is due to an out-of-bounds runtime in the Fluids subsystem.

[22:54:14] Runtime in code/controllers/subsystem/fluids.dm,199: list index out of bounds
  proc name: cancel spread (/datum/controller/subsystem/fluids/proc/cancel_spread)
  src: Smoke (/datum/controller/subsystem/fluids/smoke)
  call stack:
  Smoke (/datum/controller/subsystem/fluids/smoke): cancel spread(the smoke (/obj/effect/particle_effect/fluid/smoke/chem))
  the smoke (/obj/effect/particle_effect/fluid/smoke/chem): Destroy(0)
  the smoke (/obj/effect/particle_effect/fluid/smoke/chem): Destroy(0)
  qdel(the smoke (/obj/effect/particle_effect/fluid/smoke/chem), 0)
  /datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable): Destroy(0)
  qdel(/datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable), 0)
  RunUnitTest(/datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable), /list (/list))
  RunUnitTests()
  /datum/callback (/datum/callback): InvokeAsync()
[22:54:14] Runtime in code/controllers/subsystem/fluids.dm,199: list index out of bounds
  proc name: cancel spread (/datum/controller/subsystem/fluids/proc/cancel_spread)
  src: Smoke (/datum/controller/subsystem/fluids/smoke)
  call stack:
  Smoke (/datum/controller/subsystem/fluids/smoke): cancel spread(the smoke (/obj/effect/particle_effect/fluid/smoke/chem))
  the smoke (/obj/effect/particle_effect/fluid/smoke/chem): Destroy(0)
  the smoke (/obj/effect/particle_effect/fluid/smoke/chem): Destroy(0)
  qdel(the smoke (/obj/effect/particle_effect/fluid/smoke/chem), 0)
  /datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable): Destroy(0)
  qdel(/datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable), 0)
  RunUnitTest(/datum/unit_test/modify_fantas... (/datum/unit_test/modify_fantasy_variable), /list (/list))
  RunUnitTests()
  /datum/callback (/datum/callback): InvokeAsync()