A user pressing "next tip" will expect to cycle sequentially
through the list of tips, and not get a random one each time.

Change-Id: I331d35d623b6449a9daef407a498b4ba08eaff6f
Reviewed-on: https://gerrit.libreoffice.org/72099
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>
Reviewed-by: Heiko Tietze <tietze.heiko@gmail.com>