Hi again,
Our main DB is back on 7.8 because we just had far too many -9111 errors with 7.9. However we have 2 other databases now running with 7.9 and they run just fine.
And yes I ran the "null check" query on the 7.9 instance, we had exactly 6356 such columns.
If you have a hotfix for that problem for 7.9, we could of course install it on our 7.9 instance and test everything again (we would migrate our data again and switch again from 7.8 to 7.9).
Christophe