Right click on a text input in a widget stops working after moving a widget

[g.pabian]

After moving a widget (e.g. an image with a caption) to a different position and right-clicking on a text input, an error is thrown in the console and the right click menu doesn't show up. Issue occurs on Chrome 37.0.2062.120 (64-bit) running at Ubuntu 14.04.

Reproduction steps:

1. Open "New image plugin" sample: ​http://ckeditor.com/latest/samples/plugins/image2/image2.html
2. Move one of the images to the top of the text area.
3. Right-click on the image caption (don't select the text, just click it).

Result: No right click menu is visible and an error in the console is thrown: "Uncaught TypeError: Cannot read property 'checkReadOnly' of undefined"

Expected result: Right click menu should be opened.

[Jakub Ś]

I was able to reproduce this problem in Chrome and Chromium, on Linux only, from CKEditor 4.3 (works fine in 4.3 beta)