[Koha] Search failing only on one phrase "economics"

[Raphael Muonga]

Colleagues suddenly I am having this search problem only on this word
which was working very well last few days both in Intranet and OPAC.
But it is working okay another phrase(s).

The error I am getting is as follows in both Intranet and OPAC:-

Can't call method "as_usmarc" on an undefined value at
/usr/share/koha/lib/C4/Search.pm line 2383.


What has caused this and how can I solve it?

Thanks in anticipation.
Raphael.