Display "Sold" ribbon on sold out items

[Gonab]

Dear everyone!

 

I would like to show a "sold" ribbon over the product image on products with quantity stock at "0".

 

I opened product-list.tpl and I added this code: {if $product.quantity==0}<img src="https://www.liquorland.com.au/lle2e/PublishingImages/Sold-Out-small.png" style="position:absolute; top:0px; right:0px; "/>{/if}

 

in this position: http://gyazo.com/284af1fc131d8aa1213c47061e307c2c but is not showing on the website (http://elpatioantiguedades.com/tienda/muebles-pintados-jardin/40-pareja-de-mesitas-de-noche-decapadas-antiguas.html)

 

Hope someone will be able to help me!

 

Thanks in advance!