Error 500

after updating our php version (from 5.7 to 7.3) im getting request failed status 500, tried to downgrade to php7.2 and 7.0 but still not working

Tried mysite/wp-admin/admin-ajax.php and is returning 0

Algo i got this error from log Thu Feb 28 12:27:20.175551 2019] [:error] [pid 27462] [client 192.168.200.254:56309] PHP Catchable fatal error: Object of class WP_Term could not be converted to string in /var/www/html8/wp-content/plug
ins/ajax-search-lite/includes/classes/search/search_content.class.php on line 314, referer: mysite/url/

You can see my debug data from plugin here https://paste.ee/p/dioVS