Support loading graph without nodes coordinates

dream/platform/src/jsplumb/jsplumb.js

@@ -549,13 +549,15 @@
     node_data.name = node_data.name || class_definition.name;
     gadget.props.node_container[node_id] = node_data;
 
-    if (coordinate !== undefined) {
+    if (coordinate === undefined) {
+      coordinate = {top: 0, left: 0}
+    }
+
     node_data.coordinate = updateElementCoordinate(
       gadget,
       node_id,
       coordinate
     );
-    }
 
     // XXX make node template an option, or use CSS from class_definition
     /*jslint nomen: true*/