Update to 8.9 – problems

Hi,

I have updated my WordPress to 4.2.2 and updated the template from 8.3 to the stable 8.9 version.

I get this error:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, class ‘wlt_core_customerize’ not found in ../public_html/wp-includes/plugin.php on line 525

I tried to deactivate all 3 plugins, still got the error. Any ideas what the problem might be?

Thanks!