Merge pull request #14461 from farie82/tgui-destroy-UID-fix

Makes it so that not every datum uses an UID everytime it gets destroyed

code/controllers/subsystem/tgui.dm

@@ -126,6 +126,8 @@ SUBSYSTEM_DEF(tgui)
   * return int The number of UIs closed.
  **/
 /datum/controller/subsystem/tgui/proc/close_uis(datum/src_object)
+	if(!src_object.unique_datum_id) // First check if the datum has an UID set
+		return 0
 	var/src_object_key = "[src_object.UID()]"
 	if(isnull(open_uis[src_object_key]) || !istype(open_uis[src_object_key], /list))
 		return 0 // Couldn't find any UIs for this object.