OC_Util is better thank OCP\JSON because it'll redirect the user to the index.php instead of displaying an error

apps/impress/documentation.php

@@ -24,7 +24,7 @@
 require_once('lib/impress.php');
 
 OCP\User::checkLoggedIn();
-OCP\JSON::checkAppEnabled('impress');
+OC_Util::checkAppEnabled('impress');
 OCP\App::setActiveNavigationEntry( 'impress_index' );
 
 

apps/impress/index.php

@@ -24,7 +24,7 @@
 require_once('lib/impress.php');
 
 OCP\User::checkLoggedIn();
-OCP\JSON::checkAppEnabled('impress');
+OC_Util::checkAppEnabled('impress');
 OCP\App::setActiveNavigationEntry( 'impress_index' );
 
 

apps/impress/player.php

@@ -25,7 +25,7 @@ require_once('lib/impress.php');
 
 // Check if we are a user
 OCP\User::checkLoggedIn();
-OCP\JSON::checkAppEnabled('impress');
+OC_Util::checkAppEnabled('impress');
 
 $filename = OCP\Util::sanitizeHTML($_GET['file']);
 $title = OCP\Util::sanitizeHTML($_GET['name']);