Clockcult execute failure protection (BeeStation#10108)

code/game/gamemodes/dynamic/dynamic_rulesets_roundstart.dm

@@ -608,6 +608,11 @@
 	main_cult.setup_objectives()
 	//Create team
 	for(var/datum/mind/servant_mind in assigned)
+		if(!ismob(servant_mind?.current)) // user disconnected and was not assigned a mob.
+			log_game("DYNAMIC: Clockcult mind \"[servant_mind?.key]\" was lost during execute() - adding a cogscarab.")
+			assigned -= servant_mind
+			var/obj/effect/mob_spawn/drone/cogscarab = new(pick_n_take(spawns))
+			continue
 		servant_mind.current.forceMove(pick_n_take(spawns))
 		servant_mind.current.set_species(/datum/species/human)
 		var/datum/antagonist/servant_of_ratvar/S = add_servant_of_ratvar(servant_mind.current, team=main_cult)