Merge pull request #380 from metamaps/bug-labelsDisappearing

when a topic was deleted, renderEdgeArrows was trying to call on a topic...

app/assets/javascripts/src/Metamaps.JIT.js

@@ -1758,7 +1758,9 @@ Metamaps.JIT = {
         var posChild = adj.nodeTo.pos.getc(true);
 
         //plot arrow edge 
-        if (directionCat == "none") {
+        if (!direction) {
+            // render nothing for this arrow if the direction couldn't be retrieved
+        } else if (directionCat == "none") {
             edgeHelper.line.render({
                 x: pos.x,
                 y: pos.y

app/assets/javascripts/src/Metamaps.js

@@ -356,10 +356,13 @@ Metamaps.Backbone.init = function () {
             return Metamaps.Topics.get(this.get('node2_id'));
         },
         getDirection: function () {
-            return [
-                    this.getTopic1().get('node').id,
-                    this.getTopic2().get('node').id
-                ];
+            var t1 = this.getTopic1(),
+                t2 = this.getTopic2();
+
+            return t1 && t2 ? [
+                    t1.get('node').id,
+                    t2.get('node').id
+                ] : false;
         },
         getMapping: function () {