Fix plane when dead nested mobs merge with weeds #19603

Job	Run time
Lint with OpenDream	2m 20s
Compile Maps	1m 0s
Find Maps to Test	9s
Run Linters	2m 4s
Windows Build	1m 52s
Unit Tests (almayer) / run_unit_tests	6m 4s
Unit Tests (desert_dam) / run_unit_tests	6m 10s
Unit Tests (chinook) / run_unit_tests	5m 56s
Unit Tests (corsat) / run_unit_tests	5m 52s
Unit Tests (bigredv2) / run_unit_tests	5m 53s
Unit Tests (fiorina_sciannex) / run_unit_tests	5m 52s
Unit Tests (ice_colony_v2) / run_unit_tests	6m 12s
Unit Tests (kutjevo) / run_unit_tests	5m 56s
Unit Tests (lv522_chances_claim) / run_unit_tests	5m 52s
Unit Tests (lv624) / run_unit_tests	5m 53s
Unit Tests (new_varadero) / run_unit_tests	6m 14s
Unit Tests (prison_station_fop) / run_unit_tests	5m 54s
Unit Tests (runtime) / run_unit_tests	5m 53s
Unit Tests (shivas_snowball) / run_unit_tests	5m 53s
Unit Tests (sorokyne_strata) / run_unit_tests	5m 54s
Unit Tests (whiskey_outpost_v2) / run_unit_tests	5m 40s
Alternate Tests (515, 1610, lv624) / run_unit_tests	5m 49s
Check Alternate Tests	1s
	1h 48m 23s

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