Product.php setIsSimilarToAttributes deletes "offers"

[trebaxa]

We have to modifiy this line: $properties = array_filter($properties, 'strlen');

Because this line removes all arrays from product, which es added bei isSimilarTo property. For example: it removes "offers" , which is required for valid structured data.

Fix could be: $properties= array_filter($properties, function($var) { return !empty($var); });