front: Fix thumbnail template tag default size
front: Fix thumbnail template tag default size

Set the default size to the options dictionary instead to the given
kwargs.  This allows using the thumbnail template tag without the size
parameter as was originally intended.

suutari-ai/shoop,shoopio/shoop,suutari-ai/shoop,shoopio/shoop,shoopio/shoop,suutari-ai/shoop