Replace deprecated trigger_error calls with exceptions

models/Tag.php

@@ -276,7 +276,7 @@ class Tag
 			$data);
 
 		if (!$res)
-			trigger_error('Could not create the requested tag.', E_USER_ERROR);
+			throw new Exception('Could not create the requested tag.');
 
 		$data['id_tag'] = $db->insert_id();
 		return $return_format === 'object' ? new Tag($data) : $data;