[FIX] website_sale_digital: limit attachment search

Before this commit, in a sales order preview, a search is performed to
search all the attachments in invoiced products or free products.

Now, the search is only performed if the product is a digital product.

opw-2172563

closes odoo/odoo#43434

X-original-commit: 2c9e7832a02d2e4e2f219e979dd8ae3cbaa77bd9
Signed-off-by: Jorge Pinna Puissant (jpp) <jpp@odoo.com>

addons/website_sale_digital/controllers/main.py

@@ -45,7 +45,7 @@ class WebsiteSaleDigital(CustomerPortal):
 
         Attachment = request.env['ir.attachment'].sudo()
         purchased_products_attachments = {}
-        for product in products:
+        for product in products.filtered(lambda p: p.attachment_count):
             # Search for product attachments
             product_id = product.id
             template = product.product_tmpl_id