Fixed bug with undefined constants

editor/js/graph.js

@@ -403,12 +403,12 @@ export class Graph extends ManagedData {
         }
 
         if (item.node) {
-            return item[Graph.NODE_LABEL];
+            return item[NODE_LABEL];
         } else if (item.link) {
             return (
-                Graph.toStr(item[Graph.LINK_SOURCE]) +
+                Graph.toStr(item[LINK_SOURCE]) +
                 LINK_NAME_CONNECTOR +
-                Graph.toStr(item[Graph.LINK_TARGET])
+                Graph.toStr(item[LINK_TARGET])
             );
         } else {
             return "UNDEFINED";