Currently we return NS_ERROR_FAILURE from nsXFormsModelElement::GetInstanceDocument(), but it should actually be a DOMException per the spec. The "raises(DOMException)" is commented out in the IDL, probably because the exact type of exception is unknown? Which NS_ERROR_DOM_* should we return?
Created attachment 193143 [details] [diff] [review] Patch that reports an error While we're messing with the function, how about reporting an error to the console?
Created attachment 217029 [details] [diff] [review] Patch Returning DOM_NOT_FOUND error, and report errors.
Fixed on trunk