This fixes the crash of 'Basic IDE: Docking property browser under
object catalog' commit. The aPropertyBrowser data member was replaced by
a new-allocated pointer. We need this because toolkit releases it by
delete.
When the property browser is closed in the floating state, it tells
DialogWindowLayout to null the pointer. If the user clicks the 'property
browser' button on the toolbar, it is created again.

Change-Id: Ie842a72fe37dfdd2ed5921ffa2f1f41d3f2c51c6
Reviewed-on: https://gerrit.libreoffice.org/568Tested-by: Noel Power <noel.power@suse.com>
Reviewed-by: Noel Power <noel.power@suse.com>