Resolves: rhbz#1164614 xslt dialog crashes if there are no entries

Change-Id: Id7d967389cbc9f8ae120749bbe1c79bbbe46b212
Reviewed-on: https://gerrit.libreoffice.org/13370
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>