Error 500 During Search

I have a problem with my ojs
I have 3 journal with one instalation of ojs. I get the same problem when i try to search anything in the seacr bar. The message erro is " This page isn’t working** is currently unable to handle this request. HTTP ERROR 500"

I try to open error_log in ojs directory and my problem is not show.
i have chek display_errors is on and error_reporting is E-all

i use ojs