to make it work under gtk3

Change-Id: I4c895181af233a16292ce16b194f0a60994446fb
Reviewed-on: https://gerrit.libreoffice.org/71478
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>