Plugin breaks on PHP 71+

Hi,

On PHP71 and above the plugin breaks WordPress with a 500 error. The error log states:

PHP Fatal error: Uncaught Error: [] operator not supported for strings in /wp-content/plugins/events-maker/includes/class-query.php:551

In a different plugin the same issue was fixed. See https://dfactory.eu/support/topic/import-wp-post-views-server-error-500/

I’ve made some changes to class-query to fix, I can send a diff