Bug: delimiter disappears if any block is added after it

[aatu-ikius]

When you add a delimiter to the editor and try to add any block after it, the delimiter disappears for some reason.

Steps to reproduce

1. Add a delimiter block to the editor
2. Activate the "Add" tool on the delimiter, and select any block.

The demonstration below was recorded on the Editor.js demo located on https://editorjs.io/.