Error on Checkout

				foreach($variant->characteristics as $k => $val){
					$i = 0;
					$ordering = @$element->characteristics[$val->characteristic_parent_id]->ordering;
					while(isset($chars[$ordering])&& $i < 30){
						$i++;
						$ordering++;
					}
					$chars[$ordering] = $val;
				}

if(!empty($variant->characteristics)){
					foreach($variant->characteristics as $k => $val){
						$i = 0;
						$ordering = @$element->characteristics[$val->characteristic_parent_id]->ordering;
						while(isset($chars[$ordering])&& $i < 30){
							$i++;
							$ordering++;
						}
						$chars[$ordering] = $val;
					}
				}