Fix the height of the new search result pane.

For the bigger search filters like C++ Symbols & Files on File System
it was unusable e.g. on Mac.

Change-Id: I1839238660cc7508ada4e580388ee08d8eca8a6a
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Eike Ziller <eike.ziller@nokia.com>