diff --git a/inc/nav-walker.php b/inc/nav-walker.php
index cdf2485..605724b 100644
--- a/inc/nav-walker.php
+++ b/inc/nav-walker.php
@@ -344,13 +344,16 @@ function my_wp_nav_menu_objects_sub_menu( $sorted_menu_items, $args ) {
 			$second_level_parent = $newmenu[3][$parent_id];
 		}
 		else return array();
-		foreach($newmenu[3] as $id=>$menu_item){
-			if($menu_item != $second_level_parent) unset($newmenu[3][$id]);
+		if( isset($newmenu[3]) && is_array($newmenu[3]) ){
+			foreach($newmenu[3] as $id=>$menu_item){
+				if($menu_item != $second_level_parent) unset($newmenu[3][$id]);
+			}
 		}
-		foreach($newmenu[4] as $id=>$menu_item){
-			if(!isset($newmenu[3][$menu_item])) unset($newmenu[4][$id]);
+		if( isset($newmenu[4]) && is_array($newmenu[4]) ){
+			foreach($newmenu[4] as $id=>$menu_item){
+				if(!isset($newmenu[3][$menu_item])) unset($newmenu[4][$id]);
+			}
 		}
-		
 		foreach($sorted_menu_items as $key => $menu_item) {
 			if(!isset($newmenu[3][$menu_item->ID]) && !isset($newmenu[4][$menu_item->ID])) unset($sorted_menu_items[$key]);
 		}