tdf#141186 ensure child of collapsed expander is not mapped
If the expander is initially collapsed then when mapped all its children
are mapped too.
If they are mapped then the mnemonics of the children are taken into
account on shortcuts and non-visible children in a collapsed expander
can be triggered which is confusing.
If the expander is expanded and collapsed the child is unmapped
and the problem doesn't occur.
So to avoid the problem of an initially collapsed expander, listen to
the map event and if the expander is mapped but collapsed then unmap the
child of the expander.
Change-Id: Ib4c7a704295b338230357c4c4102a3692f8a9707
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/134453
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>