Fix warning in XEDITION skin if there are no categories

modules/board/skins/xedition/_header.html

@@ -9,6 +9,7 @@
 <!--@end-->
 <block cond="!$module_info->duration_new = (int)$module_info->duration_new">{@ $module_info->duration_new = 12 }</block>
 {@ $cate_list = array(); $current_key = null; }
+{@ $category_list = $category_list ?? []}
 <!--@foreach($category_list as $key=>$val)-->
 	<!--@if(!$val->depth)-->
 		{@