Widget: Unexpected copy of widget area block

[t-hamano]

Description

In the Widget Block Editor, widget area blocks (core/widget-area)are also subject to block selection and can be copied.
However, widget area blocks are not allowed to be inserted into the block editor, so an error occurs when pasting the block.
Also, I think the copied block HTML seems to have no use.

Step-by-step reproduction instructions

• Activate a classic theme.
• Open the widget block editor.
• Click on the title panel of the widget area and press Ctrl(Cmd) + C or Ctrl(Cmd) + X.
• Confirm that the widget area block is copied.
• Confirm that you get a message that the block is not supported when you paste in the post editor.

Screenshots, screen recording, code snippet

170079526-4061dc62-0d2d-4090-a941-7a1e87fad839.mp4

Environment info

No response

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