Theming: Fix light colored find widgets style

It is used when e.g. searching the environment widget.

Change-Id: I203b9f5e280a8f18f7a38f8e4d7b4540c79f932c
Reviewed-by: Thorben Kroeger <thorbenkroeger@gmail.com>
Reviewed-by: hjk <hjk121@nokiamail.com>