Makes from-ghost midrounds not roll if no ghosts

code/game/gamemodes/dynamic/dynamic_rulesets_midround.dm

@@ -87,6 +87,8 @@
 		var/threat = round(mode.threat_level/10)
 		if (job_check < required_enemies[threat])
 			return FALSE
+		if (length(dead_players) + length(list_observers) == 0)
+			return FALSE
 	return TRUE
 
 /datum/dynamic_ruleset/midround/from_ghosts/execute()