Make sure we try to autoload the class

lib/private/Server.php

@@ -631,7 +631,14 @@ class Server extends ServerContainer implements IServerContainer {
 			return $factory->getManager();
 		});
 		$this->registerService('ThemingDefaults', function(Server $c) {
-			if(class_exists('OCA\Theming\Template', false) && $this->getConfig()->getSystemValue('installed', false) && $this->getAppManager()->isInstalled('theming')) {
+			try {
+				$classExists = class_exists('OCA\Theming\Template');
+			} catch (\OCP\AutoloadNotAllowedException $e) {
+				// App disabled or in maintenance mode
+				$classExists = false;
+			}
+
+			if ($classExists && $this->getConfig()->getSystemValue('installed', false) && $this->getAppManager()->isInstalled('theming')) {
 				return new Template(
 					$this->getConfig(),
 					$this->getL10N('theming'),

lib/private/URLGenerator.php

@@ -30,7 +30,8 @@
  */
 
 namespace OC;
-use OCP\Defaults;
+
+
 use OCP\ICacheFactory;
 use OCP\IConfig;
 use OCP\IURLGenerator;