Placeholder shown when node has inline children

[gambolputty]

Description
The placeholder extension detects a node to be empty, when in fact it has one or multiple child inline nodes.

Steps to reproduce the bug
With Placeholder extension and Mention node:

1. Go to CodeSandbox
2. Type "@" to open the Mention menu and select an entry from the list. Hit Backspace to remove the trailing whitespace inserted by the Suggestion utility.
3. Blur the editor.
4. See the placeholder being displayed behind the mention (inline-) node.

CodeSandbox
I created a CodeSandbox to help you debug the issue: CodeSandbox

Expected behavior
The placeholder should not be displayed, because the node is not empty.

Environment?

• operating system: MacOS
• browser: Chrome, latest
• mobile/desktop: Desktop
• tiptap version: latest

Additional context / possible solution
node.childCount can be used to check, if a node has children. Maybe this should be used in here:

tiptap/packages/extension-placeholder/src/placeholder.ts

Line 43 in 2502932

const isEmpty = !node.isLeaf && !node.textContent

e.g.

node.childCount === 0