Debug lines left in the code

In the latest release you have left a line of code to write to error_log. It is totally spams the php_errors.log file

The line of code that needs to be removed is found on line 113 here:

https://plugins.trac.ww.wp.xz.cn/browser/simple-event-planner/trunk/includes/class-simple-event-planner-post-type-event-listing.php