Issue with Persistent Placeholder in Liveblocks and BlockNote when Using Multiple Clients

[devmalcolm]

Hi, i have discovered a bug in Liveblocks and BlockNote where placeholders remain visible even after I input text using features like Headings (1, 2, 3) or Bullet Lists. This issue arises when two or more clients are simultaneously interacting with the same document.

Steps to Reproduce:

• Open Liveblocks and BlockNote in multiple client sessions. (or something else that allow collaboration)
• Insert a text element that includes a placeholder, such as a Heading or a Bullet List / Numbered List.
• Type text into the newly created text element.

Expected Behavior: The placeholder should disappear once text is entered.

Actual Behavior: The placeholder remains visible behind the text I enter, leading to potential confusion about whether the text is properly recorded.

Additional Information: This issue occurs consistently with both Headings and Bullet Lists. The problem is reproducible across various client sessions. (I've tested without any clients and it seems to work without bugs)