[FIX] web: fix kanban_image for binary data

`.value` is always bin size. By using `.raw_value` we allow the condition to be
true when actually using binary data.

This solves an issue when trying to display the image for a model being created
since at that time the URL does not work yet since the model does not exist.
Eg. website_sale extra images on product.

This also prevents (potentially a lot of) unnecessary GET to fetch images for
which we already have the binary data downloaded.

Part of task 34045

PR: #30881