Gutenberg: Modifying custom class after initial update doesn't enable update button

[philbuchanan]

Describe the bug
When a user modifies a custom class on a block after the update button has been clicked within the post, the update button remains disabled.

To reproduce
Steps to reproduce the behavior:

1. Create a new page.
2. Add a block to the page (e.g. Heading).
3. Add an additional CSS class in the edit panel for the heading.
4. Save the page.
5. Without leaving the editor and coming back, attempt to edit the class you just added.
6. The update button remains disabled.

Expected behavior
I would expect that the update button would allow me to save the change to the additional class field.

Desktop (please complete the following information):

• OS: MacOS 10.14.6
• Browser: Safari
• Version: 13.0.1

Additional context

• Gutenberg v6.5.0
• Wordpress v5.2.3

[fresatomica]

We've got a user report about this here: https://twitter.com/4rchi7/status/1179273379880280064

[jorgefilipecosta]

Hi @philbuchanan, @fresatomica, thank you for reporting this issue. In my tests, it seems it was fixed and the problem should not happen when WordPress 5.4 is released.