The Events Calendar Pro 6.4.0

* Fix - Prevent fatal when not using Blocks Editor with Event Tickets and Events Calendar Pro active

* Fix - Prevent fatal happening on Widget Calendar Mini with Site Origin Page builder [122546]

* Feature - Added the "Related Events" block [118995]
* Fix - Improve the Additional Fields presentation both in the back-end and front-end [120281]
* Tweak - Changed views: `blocks/additional-fields/checkbox`, `blocks/additional-fields/dropdown`, `blocks/additional-fields/radio`, `blocks/additional-fields/text`, `blocks/additional-fields/textarea`, `blocks/additional-fields/url`, `blocks/related-events`, `blocks/related-events/event-info`, `blocks/related-events/event-thumbnail`, `blocks/related-events/event`, `blocks/related-events/title`
* Language - 1 new strings added, 50 updated, 0 fuzzied, and 0 obsoleted