Post editor crashes when clearing customizations in template editing mode.

[tellthemachines]

Description

When editing the template for a new post from the post sidebar, saving changes to the template and then clicking "clear customizations" in the top toolbar causes the editor to crash.

I've reproduced this several times, and there are two different errors that alternately appear in the console:

Uncaught TypeError: Cannot read properties of null (reading 'removeEventListener') in the <BlockPopoverInbetween> component

and

Uncaught TypeError: Cannot read properties of null (reading 'title') in the BlockParentSelector component.

Step-by-step reproduction instructions

1. Create a new post but don't publish it yet;
2. In the post sidebar, in the "Template" dropdown, click "edit template";
3. Make some changes to the template and save them;
4. In the top toolbar, open "Template Options" dropdown and click "Clear customizations";
5. Click "ok" in confirmation dialog and verify that editor crashes.

Screenshots, screen recording, code snippet

No response

Environment info

I can reproduce this both on Gutenberg trunk (running on 6.1-alpha-53810) and wordpress-develop trunk, so whatever is causing the issue must have already been backported to Core. I can't reproduce it on Gutenberg 14.1.1 running on WP 6.0.2.

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes