Converting Table block within a Group to reusable block causes Gutenberg editor to crash

[cathymcbride]

Describe the bug
Gutenberg editor crashes when converting table within a group to reusable block

Steps to reproduce the behavior:

1. Add new post.
2. Add Group block.
3. Add Table block with any number of rows and columns within the Group block.
4. Save draft.
5. Return to Posts management page.
6. Reopen the draft.
7. Click on a table cell to bring up the toolbar.
8. Click on the kebab menu.
9. Click on Add to Reusable block.

Expected behavior
Table is converted into a reusable block.

Actual behavior
editor crashes (see stack trace below)

Screenshots
If applicable, add screenshots to help explain your problem.

Editor version (please complete the following information):

• WordPress version: [e.g: 5.3.2] 5.5.3
• Does the website has Gutenberg plugin installed, or is it using the block editor that comes by default? "gutenberg plugin",
• If the Gutenberg plugin is installed, which version is it? 9.4.1

Desktop (please complete the following information):

• OS: [e.g. iOS] macOS
• Browser: not browser specific - reproed on chrome, safari and firefox

Additional context

Stack trace:
Error: An error occurred while running 'mapSelect': Cannot read property 'name' of null
The error may be correlated with this previous error:
TypeError: Cannot read property 'name' of null
at Object.current (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/block-editor/index.js?ver=fdb8c27842d6665c8f717ab07efd9458:46:2298)
at e (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:28762)
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:28927
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:23198
at Array.forEach ()
at o (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:23170)
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:20382
at p (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:11415)
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/redux-routine/index.js?ver=465b7310eb6f6a685e44cf8c6c5ce817:1:9762
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:14089

Original stack trace:
at Fe (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/data/index.js?ver=152d217f4cbf8a22c88dc20c16e8d8c1:1:28554)
at Qs (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/build/block-editor/index.js?ver=fdb8c27842d6665c8f717ab07efd9458:46:2160)
at we (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:84:293)
at He (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:97:464)
at zj (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:228:406)
at Th (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:152:223)
at tj (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:152:152)
at Te (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:146:151)
at https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react-dom.min.de439aae.js:61:68
at unstable_runWithPriority (https://modern-eagle.jurassic.ninja/wp-content/plugins/gutenberg/vendor/react.min.e713ea3b.js:25:260)

[talldan]

Initially I was unable to reproduce this in my dev environment, but then I pulled the latest code from master and was able to reproduce it. It must be something very recently introduced. Here's an non-minified stack trace:

The above error occurred in the <BlockStyles> component:
    in BlockStyles (created by BlockInspector)
    in div (created by PanelBody)
    in PanelBody (created by BlockInspector)
    in div (created by BlockInspector)
    in div (created by BlockInspector)
    in BlockInspector
    in Unknown (created by WithSelect(BlockInspector))
    in WithSelect(BlockInspector) (created by SettingsSidebar)
    in div (created by ForwardRef(Panel))
    in ForwardRef(Panel) (created by ComplementaryArea)
    in div (created by ComplementaryAreaFill)
    in SlotComponent (created by Context.Consumer)
    in Slot (created by Slot)
    in Slot (created by ComplementaryAreaSlot)
    in ComplementaryAreaSlot (created by Layout)
    in div (created by ForwardRef(InterfaceSkeleton))
    in div (created by ForwardRef(InterfaceSkeleton))
    in div (created by ForwardRef(InterfaceSkeleton))
    in div (created by ForwardRef(InterfaceSkeleton))
    in ForwardRef(InterfaceSkeleton) (created by Layout)
    in div (created by FocusReturnProvider)
    in FocusReturnProvider (created by Layout)
    in Layout (created by Editor)
    in ErrorBoundary (created by Editor)
    in BlockEditorProvider
    in Unknown (created by Context.Consumer)
    in WithRegistryProvider(BlockEditorProvider) (created by EditorProvider)
    in BlockContextProvider (created by EditorProvider)
    in EntityProvider (created by EditorProvider)
    in EntityProvider (created by EditorProvider)
    in EditorProvider (created by WithDispatch(EditorProvider))
    in WithDispatch(EditorProvider)
    in Unknown (created by WithSelect(WithDispatch(EditorProvider)))
    in WithSelect(WithDispatch(EditorProvider))
    in Unknown (created by Context.Consumer)
    in WithRegistryProvider(WithSelect(WithDispatch(EditorProvider))) (created by Editor)
    in div (created by DropZoneProvider)
    in DropZoneProvider (created by Editor)
    in SlotFillProvider (created by SlotFillProvider)
    in SlotFillProvider (created by Editor)
    in StrictMode (created by Editor)
    in Editor (created by WithDispatch(Editor))
    in WithDispatch(Editor)
    in Unknown (created by WithSelect(WithDispatch(Editor)))
    in WithSelect(WithDispatch(Editor))

[talldan]

When testing to see if this is a regression in 5.6, I was able to reproduce in both 5.5.3 and 5.6 with the plugin disabled, so maybe not a recent issue.

Not sure why I couldn't repro it at first. 🤔

[TimothyBJacobs]

For #29055 at least, I wasn't able to reproduce on 5.6.

[talldan]

I think it seems to happen with any block that has block styles when the sidebar is opened. The steps i'm using to reproduce:

1. Create a new post
2. Add a quote block
3. Save the post
4. Reload
5. Convert the quote to a reusable block
6. 💥

It looks like after the quote block has been removed and made reusable, the sidebar is still momentarily trying to show the block styles for it. The exception happens because the quote block no longer exists.

[talldan]

#29059 should fix it, but it's an unusual one.