Fix collected properties in window-property-collector.js

LayoutTests/fast/dom/Window/resources/window-property-collector.js

 function collectProperties()
 {
     // Collect properties of the top-level window, since touching the properties
     // of a DOMWindow affects its internal C++ state.
     collectPropertiesHelper(window, []);
 
     propertiesToVerify.sort(function (a, b)
     {
         if (a.property < b.property)
             return -1
@@ skipping 67 matching lines @@
         // Skip the properties which are hard to expect a stable result.
         // As for 'accessibilityController', we can hardly estimate the states
         // of the cached WebAXObjects.
         // FIXME: We can't access accessibilityController's properties here
         // because some property accesses might crash (crbug/351195).
         if (property == 'accessibilityController')
             continue;
         // As for 'localStorage', local storage is not reliably cleared between tests.
         if (property == 'localStorage')
             continue;
-        if (!object[property])
-            continue;
         path.push(property);
         var type = typeof(object[property]);
         if (type == "object") {
-            // Skip some traversing through types that will end up in cycles...
-            if (!object[property].Window
+            if (object[property] === null) {
+                emitExpectedResult(path, "null");
+            } else if (!object[property].Window
                 && !(object[property] instanceof Node)
                 && !(object[property] instanceof MimeTypeArray)
                 && !(object[property] instanceof PluginArray)) {
+                // Skip some traversing through types that will end up in cycles...
                 collectPropertiesHelper(object[property], path);
             }
         } else if (type == "string") {
             emitExpectedResult(path, "''");
         } else if (type == "number") {
             emitExpectedResult(path, "0");
         } else if (type == "boolean") {
             emitExpectedResult(path, "false");
         }
         path.pop();
     }
 }