Fix bug where scrollExecutionTree is empty

lib/tools/jsExecutionTransformer.js

@@ -121,24 +121,28 @@ var jsExecutionTransformer = function() {
             debug('JS execution transformation complete');
 
 
-            debug('Starting scroll execution transformation');
-            offenders.DOMaccessesOnScroll = JSON.parse(data.toolsResults.phantomas.offenders.scrollExecutionTree[0]);
-            if (offenders.DOMaccessesOnScroll.children) {
-                offenders.DOMaccessesOnScroll.children.forEach(function(node) {
-                    
-                    // Mark a event flag
-                    if (['documentScroll', 'windowScroll', 'window.onscroll'].indexOf(node.data.type) >= 0) {
-                        node.windowPerformance = true;
-                    }
+            if (data.toolsResults.phantomas.offenders.scrollExecutionTree) {
+                debug('Starting scroll execution transformation');
+                offenders.DOMaccessesOnScroll = JSON.parse(data.toolsResults.phantomas.offenders.scrollExecutionTree[0]);
+                if (offenders.DOMaccessesOnScroll.children) {
+                    offenders.DOMaccessesOnScroll.children.forEach(function(node) {
+                        
+                        // Mark a event flag
+                        if (['documentScroll', 'windowScroll', 'window.onscroll'].indexOf(node.data.type) >= 0) {
+                            node.windowPerformance = true;
+                        }
 
-                    // Transform domPaths into objects
-                    changeListOfDomPaths(node);
-                    
-                    // Count the number of DOM accesses, by counting the tree leafs
-                    metrics.DOMaccessesOnScroll += countTreeLeafs(node);
-                });
+                        // Transform domPaths into objects
+                        changeListOfDomPaths(node);
+                        
+                        // Count the number of DOM accesses, by counting the tree leafs
+                        metrics.DOMaccessesOnScroll += countTreeLeafs(node);
+                    });
+                }
+                debug('Scroll execution transformation complete');
+            } else {
+                debug('Could not parse scrollExecutionTree');
             }
-            debug('Scroll execution transformation complete');
 
         } catch(err) {
             throw err;