Merge pull request #6228 from MrPetovan/bug/5911-undefined-constant-DB_UPDATE_VERSION

Add DB connection status check in Update::check

src/Core/Update.php

@@ -18,6 +18,10 @@ class Update
 	 */
 	public static function check($via_worker)
 	{
+		if (!DBA::connected()) {
+			return;
+		}
+
 		$build = Config::get('system', 'build');
 
 		if (empty($build)) {