Fix find button in search window

It should use the text filled in the search entry.
And it should not close the window if nothing is found.

review3101003
(transplanted from 8b22f7366f7caeb7ecbe86c28b8b4f8f3bf32627)

--HG--
extra : transplant_source : %8B%22%F76o%7C%AE%B7%EC%BE%86%C2%8B%8BO%8F%3B%F3%26%27
Don't set missing default value to False

False is not always a good valid value for the field, so it is better to let the
field dealing with default value.

issue3643
review3281002
(transplanted from 9a16381241f48ca880e7544edeef54c255c99255)

--HG--
extra : transplant_source : %9A%168%12A%F4%8C%A8%80%E7TN%DE%EFT%C2U%C9%92U