Before this change, there was a bug in Firefox where the registered Stimulus controllers on the window.Stimulus object were never saved.
This happened because event.data.registeredControllers.constructor === Array always returned false.
For some reason, this array detection method didn't work in Firefox.
I'm not going to investigate further, since I don't think we really need this check.
Before this change, there was a bug in Firefox where the registered Stimulus controllers on the
window.Stimulusobject were never saved. This happened becauseevent.data.registeredControllers.constructor === Arrayalways returnedfalse. For some reason, this array detection method didn't work in Firefox. I'm not going to investigate further, since I don't think we really need this check.