Some ranges throw error when calling deleteContents(true)

[engineering-this]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Open https://codepen.io/jacekbogdanski/pen/XWEygOX
2. Open browser console.
3. Press button below editor.

Expected result

Editor content is removed.

Actual result

Error thrown

pen.js:13 TypeError: Cannot read property 'insertBefore' of null
    at CKEDITOR.dom.element.insertAfter (ckeditor.js:76)
    at h (ckeditor.js:149)
    at d (ckeditor.js:151)
    at CKEDITOR.dom.range.deleteContents (ckeditor.js:155)
    at CKEDITOR.dom.element.<anonymous> (pen.js:11)
    at CKEDITOR.dom.element.p (ckeditor.js:10)
    at CKEDITOR.dom.element.fire (ckeditor.js:12)
    at HTMLButtonElement.<anonymous> (ckeditor.js:68)

Other details

This is reproducible, when below criteria are met:

• There are at least two elements in editable
• Range starts at offset 0 in editable
• Range ends at last possible offset of last editable child

• Browser: Any
• OS: Any
• CKEditor version: Found in 4.11.4
• Installed CKEditor plugins: image2

[engineering-this]

Extracted from #2517 (comment)