                      this.startInterval();
                  } else {
 -                    if (this._interval) {
-+                    if (this._interval == null) {
++                    if (this._interval != null) {
                          clearInterval(this._interval);
                          this._interval = null;
                      }

              */
             startInterval: function() {
-                if (!this._interval) {
+                if (this._interval != null) {
                     var self = this;
                     var callback = function() { self._tryPreloadAttach(); };
                     this._interval = setInterval(callback, this.POLL_INTERVAL);

                 if (onAvailStack.length === 0) {
                     retryCount = 0;
-                    if (this._interval) {
+                    if (this._interval != null) {
                         clearInterval(this._interval);
                         this._interval = null;
                     } 
