Error

Hello!
I have installed WordPress 4.0 and version 2.8.12
I installed the plugin and followed the steps but I get the following error.
Warning: trim () Expects parameter 1 to be string, array Given in /html/wp-content/plugins/event-post/eventpost.php on line 250
Can you help me solve this problem please?

https://ww.wp.xz.cn/plugins/event-post/