React: Custom react tool gets deleted when subsequent block gets deleted.

## Current Situation

In my React app, I've created several custom tools that render react components. Everything works fine so far, including interactions with react, content editing (with custom edit views/states in the react component), etc.

`@editorjs/editorjs: 2.17.0` is installed.

But the following does not work.

## Current Problem(s)

### Backspace at position 0 in subsequent block

When hitting backspace, the custom block gets deleted.


(see also https://d.pr/i/DuYgCC/1zprl6UkZb)

### Deleting the last item of a list deletes the custom block


(see also https://d.pr/i/LhIjdF/lpEsyTkUPi)

## Expected Behaviour

Instead of deleting the custom blocks, they should persist.*

*Edit*: persist means they should not be deleted, just because the subsequent block gets deleted. The custom block can be deleted (eg. with the tool settings) still.

NOTE: the custom blocks **are not contenteditable**! This would lead to unwanted side-effects (eg. user can edit react content etc.).

## Example App

- https://codesandbox.io/s/editorjs-react-editor-js-example-with-custom-react-component-template-8md15

## Related Issues

- https://github.com/codex-team/editor.js/issues/810 maybe?

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As always, thank you very much for your help!