Check null capable fields in locate mode

[helmuterik]

Does anyone know how to check if a field is null when reading a
database file in locate mode?

I've opened the file with nullcap=Y but as the in_null_map part of the
RFILE struct operates on field level I can't seem to make use of it on
a certain part of the in_buf system buffer, or can I?

[helmuterik]

I had misread the documentation. The RFILE struct has of course
nothing to do with locate or move mode, so it's real easy to just
check the byte corresponding to a column in the in_null_map and check
if it's '1'.