Type of report

Bug

Provide detailed reproduction steps (if any)

In Sample Source Code in Mentions, Tags and Emoji example this CSS file https://ckeditor.com/docs/vendors/4.14.1/ckeditor/assets/mentions/contents.css throws 404 error.

In my case, when both nextContents and this.lastDeltaChangeSet are undefined, I get this error. It happens in a real scenario when I switch between 2 records, and component.js componentWillReceiveProps gets called

From component.js:

if (nextContents === this.lastDeltaChangeSet) {
        console.error(nextContents, this.lastDeltaChangeSet)
        throw new Error(
          'You are p

-- Bug Report --

Expected Behavior

Placeholder is not present when there is a list item bullet/number in the editor.

Current Behavior

Placeholder and list element are both present within the editor.

Steps to Reproduce

1. Within a megadraft editor, add any number of li elements
2. Highlight the list items
3. Press 'delete'
4. You should see the li element overlapping with