Warning line in Apache error log

Im getting a lot of:
“PHP Warning: strstr(): Empty needle in /var/www/html/wp-content/plugins/events-manager/em-posts.php on line 257”

in the Apache error log.
I have compared this plugin files against the latest and there is no changes.

Is there anything I can do ??

https://ww.wp.xz.cn/plugins/events-manager/