Are you reporting a feature or a bug?

Bug

Check if the issue is already reported

https://dev.ckeditor.com/ticket/14534

Provide detailed reproduction steps (if any)

1. Open Source.
2. Close Source.
3. Open "Style"
4. Open Source.
5. Close Source.
6. Open "Style" (Error should happen now)

Expected result

No error being thrown

Actual result

On Chrome you get the following error:
ckeditor.js:439 Uncaught TypeError: Cannot read property 'blockLimit' of null

Other details

• Browser: Chrome
• OS: Any
• CKEditor version: 4.4.6+
• Installed CKEditor plugins: N/A