[IE] Error throw after switching between source mode and then click styles button

[Artur Delura]

Browser: [IE 10...11]

Since: 4.2.1

1. Open sample: 4.4.4/standard/ckeditor/samples/uilanguages.html
2. Make some selection.
3. Go to Source mode.
4. Switch back to Edit mode.
5. Click on Styles button.

Actual result: Error is thrown in console.

Could not get „blockLimit” property of null or undefined. core/style.js:373

[Jakub Ś]

Problem can be reproduced from CKEditor 4.2 in all versions of IE.

[Jakub Ś]

Problem can also be reproduced from CKeditor 4.4.6 in Chrome:

1. Open CKEditor
2. Switch to source mode.
3. Delete all contents.
4. Switch back to WYSIWYG mode, but don't focus the editor.
5. Click any of the combo boxes.

[Jakub Ś]

The Chrome part is being fixed in #14534.