Error on arrow-down on last row

When executing the following SQL @ mySql:
select datediff(c.validTo, c.validFrom) diff, c.* from ct_certificate c
having diff<1000
order by c.validTo;

I scroll down to the last row. If I (by accident) press arrow-down I get an error:
Grid editing error
Column #0 has an undefined origin: diff
Screenshot can be provided.

In the "Data" tab or in a "Query" tab?

Query tab.