Hi hbgdio,
Good catch: I’ll be sure to report that. In the interim I would recommend the first or both of the following:
1. Although a warning correctly makes alarm bells ring in fact in this particular scenario PHP resolves the problem without any need for further intervention, so, certainly on your production or “live” site, all you really need to do is turn off the display of errors – which is a recommended practice in any case.
2. You could put a temporary fix in place quite safely by adding a couple of lines of code within a template override, which I’ll detail below.
Within your theme you would need an events directory, and that would need to contain a community sub-directory. You should then copy to that location the event-form.php template (you can find the original in plugins/the-events-calendar-community-events/views).
Next, please locate the following line of code (around line 102) in your custom copy of :
$this->formEventDetails( $event );
Add some new lines just before it, as follows:
global $post;
if (is_null($post)) $post = new stdClass;
Does that help at all?