Fix key mapping based on summary column

If we move the summary column below num columns data queries
for this column fail. This breaks for example the
certificatelineedit in Kleopatra.

The summary column is still hidden because we do not set
header data.

GnuPG-Bug-ID: T4569

This fixes: 4847fcc2

Merge is not neccessary as 4847fcc2 was not included
in any branch so far.