TypeError: Cannot read property 'length' of undefined Gutenberg 4.3.0

[mertcangokgoz]

Describe the bug

It gives an error and does not open the page

To Reproduce

1. Go to posts and create new post
2. White screeen with wordpress posts area(wp-admin/post-new.php) and it gives an error

Expected behavior
normal editor func

Screenshots

Desktop (please complete the following information):

• OS: Windows 10
• Browser Google Chrome
• Version 70.0.3538.102

Additional context

Plugins

Redis Extension: 4.1.1
CloudFlare: Yes
Predis Client: 1.1.1
PHP Version: 7.2
Multisite: No

[designsimply]

Are those plugins all active? I noticed there's one called "Disable REST API" and Gutenberg does require the REST API to be enabled. Can you try deactivating and deleting the "Disable REST API" plugin as a first troubleshooting step? You may need to clear cache after making the change. If that doesn't help, try temporarily deactivating the Shield Security plugin as a next step.

I am noting the errors from the first screenshot in plain text for reference:

Uncaught TypeError: Object(…) is not a function
TypeError: Cannot read property 'length' of undefined
Uncaught (in promise) TypeError: Cannot read property 'length' of undefined"

[mertcangokgoz]

@designsimply I tried 2 times, the problem doesn't change. I have this problem only when adding new content

sometimes it gives error when adding links.(existing content)

[designsimply]

It's possible that one of your other plugins has a conflict. In my experience, plugin conflicts are a good thing to check first but it's also possible a web server configuration could be a conflict. Is there any chance you are able to test with all other plugins turned off temporarily as a more involved troubleshooting step?

[mertcangokgoz]

Gutenberg 4.2.0 works like a charm but in 4.3.0 (with same configuration & plugins) throws error. Problem may in changes.