After installing and running I got this error while searching the catalog

[Hoangthaikt07]

After installing and running I got this error while searching the catalog . Pls show me how to fix that bug

[Hoangthaikt07]

The steps I installed on Koha 20.05.2:
mkdir /usr/share/koha/lib/Koha/Illbackends
git clone https://github.com/PTFS-Europe/koha-ill-koha
ln -s /home/koha/illbackends/koha-ill-koha /usr/share/koha/lib/Koha/Illbackends/Koha

add code into /etc/koha/site/dl/koha.conf
<interlibrary_loans>

<backend_directory>PERL_MODULE_DIR/Koha/Illbackends</backend_directory>

<staff_request_comments>hide</staff_request_comments>

<reply_date>hide</reply_date>

<digital_recipient>branch</digital_recipient>

<partner_code>ILLLIBS</partner_code>
DL
</interlibrary_loans>

- config load package in /usr/share/koha/lib/Koha/Illrequest.pm add 1 line below use C4 : 
use Koha::Illbackends::Koha::Base;