In SVN revision 815602 (http://firstname.lastname@example.org/msg13879.html) some new code is added.
This introduces a new bug where a null button is added to the form. This gives an error in Safari and Firefox and results in a form that doesn't submit.
In the code above, form.appendChild(btn) is called. In my case, the btn is not created yet, because the "if" statement is skipped (submitButton == null).
This results in an error.
I think the form.appendChild(btn) line needs to be inside the "if" block, so it is not called when the btn does not exist.