Hey @Dave,
Thanks for sharing this! I didn’t realize you were using the 4.0 Release Candidates of the core plugin and of Events Calendar Pro.
To prevent this error, please use the Release Candidates of all your other Tribe plugins, too – so, head to https://theeventscalendar.com/my-account/downloads/ and get [then install] the 4.0 Release Candidates for Filter Bar.
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If you would like, you can also get rid of WooCommerce Tickets and install the 4.0 Release Candidates for both “Event Tickets” and “Event Tickets Plus” – these are two new plugins that are replacing the old per-platform add-ons we made. So instead of having WooCommerce Tickets, then “EDD Tickets”, then “Shopp Tickets”, et cetera, starting with The Events Calendar 4.0 we’re just going to have Event Tickets and Event Tickets Plus.
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But doing the tickets-related changes are up to you! Regardless of what you do regarding tickets: to suppress this notice about Filter Bar, download and install the 4.0 Release Candidate of Filter Bar.
Cheers!
George