--- module_builder/includes/module_builder.pages.inc	2014-09-19 13:01:08.000000000 +0530
+++ module_builder.pages.inc	2014-11-19 15:58:45.000000000 +0530
@@ -81,6 +81,10 @@
       return $form;
     }
   }
+  if(empty($mb_task_handler_generate)){
+    drupal_set_message(t("Can't read or write to sites/default/files, Please check the permissions."), 'error');
+    return $form;
+  }
 
   $root_generator = $mb_task_handler_generate->getRootGenerator();