views: ignore image datasize check if datasize is zero

Check the restored image fits in the target partition only if
the datasize value is not zero. Proceed with the check before
the image/restore request otherwise.

ogcp/views.py

@@ -781,7 +781,7 @@ def action_image_restore():
 
         image_datasize = int(image['datasize'])
         part_size = int(part_size) * 1024
-        if image_datasize > part_size:
+        if image_datasize and image_datasize > part_size:
             flash(_(f'The image size is bigger than the target partition'), category='error')
             return redirect(url_for('commands'))