Search in table


I implemented a search functionalty for table entries in my application.
My example was the com.vaadin.demo.tutorial.addressbook search!

My problem:
When I add one or two filter like:

Everythink is O.K.

But when I add a third filter like

My search result is only the same: only the rows where the columns not empty!
And when I will list all rows, I clear all fields, it does not work too, I got the same search result, each time!
What is my error?



implement a workarround:

But is necessary only in this case, why? I does not understand!