AJAX post but only got a 500 error - 5.0 Beta1

[foreverpinetree]

Just tesed with wp5.0-Beta1. My theme includes a page builder, it disables Gutenberg (use 'use_block_editor_for_post' filter) for some specified pages. It needs to connect the backend via AJAX when editing these pages, but everytime I opened the builder and only got a 500 error.

Error logs:
POST http://localhost/xampp/test/wp5.0/wp-admin/admin-ajax.php 500 (Internal Server Error)

[30-Oct-2018 08:57:54 UTC] PHP Fatal error: Uncaught Error: Call to a member function is_block_editor() on null in D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\script-loader.php:2194 Stack trace: #0 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\class-wp-hook.php(286): wp_common_block_scripts_and_styles('') #1 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\class-wp-hook.php(310): WP_Hook->apply_filters('', Array) #2 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\plugin.php(453): WP_Hook->do_action(Array) #3 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\script-loader.php(2040): do_action('wp_enqueue_scri...') #4 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\class-wp-hook.php(286): wp_enqueue_scripts('') #5 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\class-wp-hook.php(310): WP_Hook->apply_filters(NULL, Array) #6 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\plugin.php(453): WP_Hook->do_action(Array) #7 D:\xampp\htdocs\xampp\test\wp5.0\wp-includes\general-template.php(2614): do_action('wp_head')

[designsimply]

Noting that if this problem happens only with WP 5.0 betas and not with the standalone Gutenberg plugin, then we will want to report the issue at https://core.trac.wordpress.org/

Before we do that, would it be possible for you to provide some better testing steps including some basic code snippets that show the problem a bit better?

[foreverpinetree]

I will report to there and provide more info, thank you. I close this issue.