Filters all empty translations from a property.
This is used if it is important to show a text, but not all translations are filled in.
The filter takes as input a resource or other variable and as argumnent the property to be shown.
Example usage:
{{ id|trans_filter_filled:`body` }}
If the resource id has the body property:
{trans, [{en, <<>>}, {nl,<<"Hallo">>}]}
Then this will show Hallo, even if the language is set to en.