Classic Editor breaks - WP 4.9.6+Gutenberg+Yoast

[maddisondesigns]

Describe the bug
I just updated one of my sites in my dev environment to WP 4.9.6 and the Classic Editor no longer shows the toolbars, or loads any content.

To narrow down the issue I deactivated all plugins except for Gutenberg and switched my theme to TwentySeventeen.

It seems to be an issue with Yoast. Disabling all plugins except for Gutenberg and it works fine.
As soon as I activate Yoast, the content and TinyMCE no longer load.

The console shows the following error:

Loading failed for the <script> with source “http://dev.maddisondesigns.com/wp-content/plugins/gutenberg/vendor/themes/modern/theme.min.js?wp-mce-4711-20180425”.

To Reproduce
Steps to reproduce the behavior:

1. Activate Yoast SEO
2. Update WP to 4.9.6
3. Try to create a new Post using the Classic Editor

Expected behavior
The TinyMCE Editor should load properly with all the toolbars and the content should load

Screenshots

macOS Sierra 10.12.1 (16B2659)
Firefox Quantum 60.0 (64-bit)

WordPress 4.9.6
Gutenberg 2.8.0
Yoast SEO 7.5.1

[bobbingwide]

Related #4678 ?

[maddisondesigns]

@bobbingwide looks like a different issue to me

[danielbachhuber]

I'm not able to reproduce this issue locally against trunk and Gutenberg 2.9. Can you do a bit more debugging to see if you can pull up more details?

[maddisondesigns]

It's looking for a file that doesn't exist. It's looking for theme.min.js in the wp-content/plugins/gutenberg/vendor/themes/modern/ folder but there are no sub-folders under the vendor folder, within the Gutenberg plugin.

If I view the page source I can see a JavaScript reference to the TinyMCE Modern theme and considering part of the url above is looking for the /vendor/themes/modern/folder, I'm pretty confident in saying that it's related.

In WP Core there's a wp-includes/js/tinymce/themes/modern/theme.min.js file. Gutenberg is looking for that same file in the plugin folder but it's not there.

Lastly, there's a couple of ACF fields on the page, but the issue occurs even when ACF is deactivated, so it's obviously nothing to do with ACF.

[maddisondesigns]

Have also updated to Gutenberg 2.9.0 and the same issue occurs

[danielbachhuber]

Related #6847