No need for being protected.

apps/contacts/lib/app.php

@@ -164,7 +164,7 @@ class OC_Contacts_App {
 	 * @brief returns the default categories of ownCloud
 	 * @return (array) $categories
 	 */
-	protected static function getDefaultCategories(){
+	public static function getDefaultCategories(){
 		return array(
 			(string)self::$l10n->t('Birthday'),
 			(string)self::$l10n->t('Business'),