I got the similar issue only in IE10 browser. I found that the issue is because of the browser compatibility. I have posted this issue already https://forums.oracle.com/thread/2537926
Actually this thing does relate to browser as it is consistent with Chrome, Firefox , IE 10.
Rich Text editor and DA compatible with other browsers like Chrome, Firefox, IE8, IE9.. But I got the an issue in IE10 browser only. In my application, I got the below error while debugging script in IE10,
SCRIPT5007: Unable to get property '1' of undefined or null reference
I am not sure whether its a browser issue or not. If you got the solution please let me know.
It has been classified as Bug. Its number is: 17065043.