Why does Individual column filtering (select inputs) not go back to showing all entries?

kswilson

I've been looking at the example given under Individual column filtering (select inputs):
http://datatables.net/examples/api/multi_filter_select.html

If I select say 'London', it correctly shows all the 'London' rows. If I go back and select 'blank', no rows at all show. If you use more than one select box, no rows show ever again, and a page refresh is required.
Is this the intended behaviour, or a bug?