refs #99, check for a valid sourceId on error

@@ -192,6 +192,7 @@ phantom.loadCasper = function loadCasper() {
      * @param  Function  callback  An optional callback
      */
     phantom.processScriptError = function processScriptError(error, file, callback) {
+        console.log(error, file, callback)
         if (error.sourceId && !this.sourceIds.hasOwnProperty(error.sourceId)) {
             this.sourceIds[error.sourceId] = file;
         }