add a proc to get objs + fix obj check (#29194)

code/game/gamemodes/objective.dm

@@ -119,7 +119,7 @@ GLOBAL_LIST_INIT(potential_theft_objectives, (subtypesof(/datum/theft_objective)
 	for(var/datum/mind/M in get_owners())
 		if(possible_target == M)
 			return TARGET_INVALID_IS_OWNER
-		if(possible_target in M.targets)
+		if(possible_target in holder.get_targets())
 			return TARGET_INVALID_IS_TARGET
 	if(SEND_SIGNAL(src, COMSIG_OBJECTIVE_CHECK_VALID_TARGET, possible_target) & OBJECTIVE_INVALID_TARGET)
 		return TARGET_INVALID_BLACKLISTED

code/game/gamemodes/objective_holder.dm

@@ -55,6 +55,12 @@
 /datum/objective_holder/proc/get_objectives()
 	return objectives
 
+/**
+ * Get all of our targets
+ */
+/datum/objective_holder/proc/get_targets()
+	return assigned_targets
+
 /**
  * Replace old_objective with new_objective
  */