Use an already existing variable instead of calling a function twice..

modules/doc/application/controllers/ModuleController.php

@@ -49,7 +49,7 @@ class Doc_ModuleController extends DocController
     {
         $moduleManager = Icinga::app()->getModuleManager();
         $modules = array();
-        foreach (Icinga::app()->getModuleManager()->listEnabledModules() as $module) {
+        foreach ($moduleManager->listEnabledModules() as $module) {
             $path = $this->getPath($module, $moduleManager->getModuleDir($module, '/doc'), true);
             if ($path !== null) {
                 $modules[] = $module;