[Koha] error from C4::Context

Hello everybody, I noticed that saving MARC subfield structure for any tag raise an error in the /var/log/koha/library/intranet-error.log the error is: in Koha 3.22 Use of uninitialized value in string eq at /usr/share/koha/intranet/cgi-bin/admin/marc_subfields_structure.pl line 292 in Koha 16.05.3 Use of uninitialized value in string eq at /usr/share/koha/intranet/cgi-bin/admin/marc_subfields_structure.pl line 288 and the line contains: unless ( C4::Context->config('demo') or C4::Context->config('demo') eq 1 ) { hope this is not a problem ciao tommaso