CKEditor setData() changes content but throws error

I have the following text area defined in my JSP page:

<textarea id="edit_subtaskstep_notes" name="edit_subtaskstep_notes" rows="15" cols="50"></textarea>

In my js file I am setting the content data as such:

CKEDITOR.instances.edit_subtaskstep_notes.setData("Hello World");

This successfully sets the ckeditor text box to contain "Hello World" when run but after this line is executed the following error is thrown in my output window:

Uncaught TypeError: undefined is not a function (14:21:03:488 | error, javascript)
at (anonymous function) (:197:29)

If I remove that line the error goes away but the data is no longer set. As it "seems" to work since the data is getting set is this some kind of bug with CKEditor v4? I'm trying to trouble shoot a key event focus bug having to do with Bootstrap modals but need to try and eliminate this one before proceeding.