FIX bad check on if in get_all_ways

htdocs/categories/class/categorie.class.php

@@ -11,6 +11,7 @@
  * Copyright (C) 2015       Raphaël Doursenaud      <rdoursenaud@gpcsolutions.fr>
  * Copyright (C) 2016       Charlie Benke           <charlie@patas-monkey.com>
  * Copyright (C) 2018-2022  Frédéric France         <frederic.france@netlogic.fr>
+ * Copyright (C) 2023		Benjamin Falière		<benjamin.faliere@altairis.fr>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -1463,7 +1464,7 @@ class Categorie extends CommonObject
 		$ways = array();
 
 		$parents = $this->get_meres();
-		if (!empty($parents)) {
+		if (is_array($parents)) {
 			foreach ($parents as $parent) {
 				$allways = $parent->get_all_ways();
 				foreach ($allways as $way) {