uui: HIG fixes

Change-Id: I92045fe661e4d1d667c860dfd47559d2303ca531
Reviewed-on: https://gerrit.libreoffice.org/13301
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>