Were failing to show, with this warning:

Gdk-WARNING **: Tried to map a popup with a non-top most parent

Change-Id: Ib68b5fc9b3edb3d25a23b66397c13833a4d080ac
Reviewed-on: https://gerrit.libreoffice.org/42936Reviewed-by: Maxim Monastirsky <momonasmon@gmail.com>
Tested-by: Maxim Monastirsky <momonasmon@gmail.com>