Fixed unset_attribute

bootstrap/modelling.alc

@@ -242,7 +242,8 @@ Void function unset_attribute(model : Element, element : String, attribute : Str
 		attr_link = set_pop(attr_links)
 		dict_delete(model["type_mapping"], read_edge_dst(model["model"][attr_link]))
 		dict_delete(model["type_mapping"], model["model"][attr_link])
-		delete_element(read_edge_dst(model["model"][attr_link]))
+		dict_delete(model["model"], reverseKeyLookup(model["model"], read_edge_dst(model["model"][attr_link])))
+		delete_element(model["model"][attr_link])
 
 	return!