Fix issue CSV export failing for some projects
Some imported projects have NULL values for label_links.label_id
for
some reason. This caused the issue export CSV to fail because the
exporter attempted to sort an array containing string values and nil
values.
We should clean up the database entries (#197307) for this with a NOT NULL constraint, but this may require some careful consideration. For now, to make exports work again, we just reject any invalid label links.
Edited by Stan Hu