og:image was not defined. itok token issue?

I have a site where everything works ok thanks to this module but I have a doubt about the og:image property:
Facebook scraper tells me that everything is ok except the image property.

This is the test link: http://www.farmacialevorato.it/vicks-vaporub-unguento

In the source of this link I see:

Facebook scraper tells me:
"og:image was not defined, could not be downloaded or was not big enough. Please define a chosen image using the og:image metatag, and use an image that's at least 200x200px and is accessible from Facebook. Image 'http://www.farmacialevorato.it/sites/default/files/field/image/1024px-Vi...' will be used instead. Consult http://developers.facebook.com/docs/sharing/webmasters/crawler for more troubleshooting tips."

Even if the image is accessible with the "itok" GET variable, is it possible to obtain a clean url of the image?