[Koha] need help in error in koha 3.6.4

hi alli have system running on koha 3.6.4 with no zebrasuddenly message appear when we are saving bib records the message Software error:Can't call method "as_usmarc" on an undefined value at /usr/share/koha/lib/C4/Search.pm line 2524.did any one faced this error before i need to solve this problemthanks for your help Mohamed El Zalabany Integrated library systems consultant mh_zalabany@hotmail.com Mobile: 0111291444