Marker objective checks

code/controllers/subsystem/minimap.dm

@@ -321,6 +321,22 @@ SUBSYSTEM_DEF(minimaps)
 		for(var/flag in GLOB.all_minimap_flags)
 			minimaps_by_z["[z_level]"].images_assoc["[flag]"] -= source
 
+/// Checks if the source has a marker already set
+/datum/controller/subsystem/minimaps/proc/has_marker(atom/source)
+	var/turf/turf_gotten = get_turf(source)
+
+	if(!turf_gotten)
+		return
+
+	var/z_level = turf_gotten.z
+
+	if(minimaps_by_z["[z_level]"])
+		for(var/flag in GLOB.all_minimap_flags)
+			if(source in minimaps_by_z["[z_level]"].images_assoc["[flag]"])
+				return TRUE
+
+	return FALSE
+
 /**
  * Fetches a /atom/movable/screen/minimap instance or creates on if none exists
  * Note this does not destroy them when the map is unused, might be a potential thing to do?

code/modules/admin/game_master/game_master.dm

@@ -242,20 +242,19 @@ GLOBAL_VAR_INIT(radio_communication_clarity, 100)
 			return TRUE
 
 		if(OBJECTIVE_CLICK_INTERCEPT_ACTION)
-			if(object in GLOB.game_master_objectives)
+			var/turf/object_turf = get_turf(object)
+
+			if(!object_turf)
+				return TRUE
+
+			if(SSminimaps.has_marker(object))
 				if(tgui_alert(user, "Do you want to remove [object] as an objective?", "Confirmation", list("Yes", "No")) != "Yes")
 					return TRUE
 
 				SSminimaps.remove_marker(object)
 				GLOB.game_master_objectives -= object
 				return TRUE
 
-			var/turf/object_turf = get_turf(object)
-			if(!object_turf)
-				return TRUE
-
-			var/z_level = object_turf.z
-
 			if(tgui_alert(user, "Do you want to make [object] an objective?", "Confirmation", list("Yes", "No")) != "Yes")
 				return TRUE
 
@@ -277,6 +276,11 @@ GLOBAL_VAR_INIT(radio_communication_clarity, 100)
 
 			background.overlays += icon
 
+			var/z_level = object_turf?.z
+
+			if(!object || !z_level)
+				return
+
 			SSminimaps.add_marker(object, z_level, MINIMAP_FLAG_USCM, given_image = background)
 
 			/// objective_info needs to be implemented both in the game master menu and overwatch TGUI