Merge pull request #1804 from haegemon/develop

fix output of function isDisabled in accordance to phpdoc and function naming

modules/system/classes/PluginManager.php

@@ -457,6 +457,7 @@ class PluginManager
         if (array_key_exists($code, $this->disabledPlugins)) {
             return true;
         }
+        return false;
     }
 
     /**