out of stock items

The out of stock message is used on the product page BEFORE the product is added to the cart.
IF you use the direct HTML link, that check isn't done and the product is added to the cart and a later check removes the product from the cart and the "The cart is empty" message is displayed.

Could you try to edit the file administrator/components/com_hikashop/classes/cart.php and add the code:
if(empty($quantity)){
$app =& JFactory::getApplication();
$app->enqueueMessage(JText::sprintf('NOT_ENOUGH_STOCK_FOR_PRODUCT',$product->product_name));
}

after the line:
if($product->product_quantity>=0 && $product->product_quantity<$quantity) $quantity = $product->product_quantity;