ckeditor Error code: editor-destroy-iframe

I see the following in the console every time I edit a field using the ckeditor plugin.

[CKEDITOR] Error code: editor-destroy-iframe.
[CKEDITOR] For more information about this error go to http://docs.ckeditor.com/#!/guide/dev_errors-section-editor-destroy-iframe
ckeditor.js:238 Uncaught TypeError: Cannot read property 'isInline' of null
    at CKEDITOR.focusManager.d (ckeditor.js:238)
    at CKEDITOR.focusManager.<anonymous> (ckeditor.js:238)
    at ckeditor.js:28

Doesn't seem to cause any issues. Thought I would post it in case the plugin needs changing or maybe I missed something in my config.

Kevin