Can't insert widget if nested editable is in path

[Comandeer]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Open https://jsfiddle.net/Comandeer/zf5eu26g/
2. Start selecting from right text under the widget and end on bottom of the widget.
3. Try to insert new image widget into the current selection.

Expected result

Image can be inserted.

Actual result

Image button is disabled. In fact most of editor's features is disabled, as selection's beginning is anchored inside nested editable (caption in this case).

Other details

• Browser: Safari
• CKEditor version: 4.5.0+
• Installed CKEditor plugins: widget, image2

[f1ames]

Same happens for Firefox.

[jacekbogdanski]

Duplicate of #2517