Remember palette selection after the popup is destroyed

Change-Id: Iecd7fd4aa89cf9d2d6842c5b544d037df6818aaf
Reviewed-on: https://gerrit.libreoffice.org/27474Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>