?? marker from IF statment PS1.7.7.8

[AHO500]

If some one could help me with this, i'am trying to insert a custom link based of the reference number of the product .
And only to products in a parent category .

This code in catalog/products.tpl

{if $category->id_parent == 5}
        <div id="installation"><a href="https://instructions.brp.com/content/instruction-sheet/sv_SE/e-instruction.html#tab=1&sku={$product.reference|escape:'htmlall':'UTF-8'}" target="_blank">Installationsguide</a></div>
       
 {/if}

it works on the product page but i get 2 questionmarks before the Link on the page?