I don't think so. From mozilla: Prior to Firefox 6, the browser would throw if the useCapture parameter was not explicitly false. Prior to Gecko 9.0 (Firefox 9.0 / Thunderbird 9.0 / SeaMonkey 2.6), addEventListener() would throw an exception if the listener parameter was null; now the method returns without error, but without doing anything.

I think addEventListener is a typo, meant removeEventListener. Could break someone, but TBH, the odds of those being null when the object is destroyed are low (oh perhaps with a URL fetch that never returns or something.)