[bug]: After deleting the last group on a page, there's a leftover empty block.

Describe the bug

After deleting last group in a page, there's a leftover empty block.

To Reproduce

1. make sure there is only one group in the current page.
2. delete this group by clicking the group handle and select "Delete" from the menu.
3. A block handle (3 dots) is leftover and cannot be delete or inserted contents.

Screenshots

https://user-images.githubusercontent.com/132558/182771514-181de25e-7912-4c9c-b372-e4848d5fbf32.mov

Expected behavior

There should not be any leftover block.

Platform

macOS

Browser

Chrome and Safari

Additional context

No response

done