Duplicating multiple blocks using shortcut keys causes the screen to crash with a fatal error.

[ddryo]

Editing screen crashes when copying using the "Shift + command + D" shortcut key with multiple blocks selected.

However, when you select "Duplicate" from the toolbar menu and copy, it works normally.
Also, it was possible to duplicate a single block with a shortcut key.

Screenshots
Crashed screen...

To reproduce
Steps to reproduce the behavior:

1. Select multiple blocks by drag & drop
2. Try to duplicate using the shortcut key ("Shift + command + D").
3. Editing screen crashes.

Environment:

• OS: Mac OS Catalina
• Browser: Chrome 80.0.3987.162
• WP Version: 5.4
• Gutenberg Version: 7.8.1

---

This is a very serious problem.
If you get this error, your work will not be saved.

People who are used to using shortcut keys will move their hands before thinking.
The screen crashes and when you notice everything is too late.

[ddryo]

When I clicked "Coppy Error", I got the following message.

TypeError: Cannot read property 'contains' of null
at http://gutenberg.wp/wp-includes/js/dist/block-editor.min.js?ver=704b9a6d689b18b6982a8b2ae902e7ec:50:132051
at Vb (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:104:431)
at Xi (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:151:136)
at unstable_runWithPriority (http://gutenberg.wp/wp-includes/js/dist/vendor/react.min.js?ver=16.9.0:26:340)
at Ma (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:52:280)
at Yb (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:150:420)
at O (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:120:254)
at ze (http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:118:14)
at http://gutenberg.wp/wp-includes/js/dist/vendor/react-dom.min.js?ver=16.9.0:53:49
at unstable_runWithPriority (http://gutenberg.wp/wp-includes/js/dist/vendor/react.min.js?ver=16.9.0:26:340)

[ddryo]

Additional information.

Maybe this is a browser dependent bug.
When confirmed on Safari, it did not reproduce.

[torounit]

Crashed too in 5.4 ( Occurs when Gutenberg 7.8 is enabled or disabled.).

Crash when duplicating with text in selected.

OS: Mac OS Catalina
Browser: Chrome 80.0.3987.162 and firefox 74.0
WP Version: 5.4
Gutenberg Version: 7.8.1