Advanced Custom Fields Pro 6.4.0.1

* Security - ACF Free now uses its own update mechanism from WP Engine servers

* Security - Newly added fields now have to be explicitly set to allow access in the content editor (when using the ACF shortcode or Block Bindings) to increase the security around field permissions. [See the release notes for more details](https://www.advancedcustomfields.com/blog/acf-6-3-6/#field-value-access-editor)
* Security Fix - Field labels are now correctly escaped when rendered in the Field Group editor, to prevent a potential XSS issue. Thanks to Ryo Sotoyama of Mitsui Bussan Secure Directions, Inc. for the responsible disclosure
* Fix - Validation and Block AJAX requests nonces will no longer be overridden by third party plugins
* Fix - Detection of third party select2 libraries will now default to v4 rather than v3
* Fix - Block previews will now display an error if the render template PHP file is not found

* Fix - The ACF Shortcode now correctly outputs a comma separated list of values for arrays
* Fix - ACF Blocks rendered in auto mode now correctly re-render their previews after editing fields
* Fix - ACF Block validation no longer raises required validation messages if HTML will automatically select the first value when rendered
* Fix - ACF Block validation no longer raises required validation messages if a default value will be rendered as the field value
* Fix - ACF Block validation no longer raises required validation messages for fields hidden by conditional logic when adding a new block