When I search the books, I faced the issue Software error: Can't call method "data" on an undefined value at /usr/share/koha/lib/C4/Search.pm line 1709.
Hi, this is usually a problem related to data or setup. Without more information on your exact version, the way you installed and how you set things up, we won't be able to help fix the issue. I recommend asking on the mailing list with the information listed above: https://koha-community.org/support/koha-mailing-lists/ Or joining the Koha IRC chat: https://koha-community.org/get-involved/irc/