returns a 501 instead of exception if app is not installed - #13088

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>

public.php

@@ -68,7 +68,8 @@ try {
 	OC_App::loadApps(array('filesystem', 'logging'));
 
 	if (!\OC::$server->getAppManager()->isInstalled($app)) {
-		throw new Exception('App not installed: ' . $app);
+		http_response_code(501);
+		exit;
 	}
 	OC_App::loadApp($app);
 	OC_User::setIncognitoMode(true);