Resolve "Classes without teachers break import"

Closes #32 (closed)

added part::backend prio::1 source::customer type::bug labels

assigned to @hansegucker

added 2 commits

• 99bdf918 - Check if a class has class teachers before trying to import them
• d15e6819 - Update changelog

Compare with previous version

marked this merge request as ready

assigned to @nik and unassigned @hansegucker

merged

mentioned in commit 7f813706