fdo#76953: cannot start show at selected slide

It was worked only in slide sorter view properly.
It seems it leads undefined behaviour when a menu item
is in the menubar.xml but has no definition in *.sdi file.
I experienced that on windows menu item was disabled
on linux it was enabled.

Change-Id: Iba4dd1cbac60a3b3350604d64d60d10d050a4e2b
(cherry picked from commit e20876b37d203642b5aa81a2d6c93979600376ed)
Reviewed-on: https://gerrit.libreoffice.org/9577
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>