Adding optional error to KeyStatusesChangedEvent type

[ed0wolf]

The ProtectionController can emit this event with an error, when the current license expires:

1. dash.js/src/streaming/protection/controllers/ProtectionController.js

   Line 635 in 75cf1a5

   eventBus.trigger(events.KEY_STATUSES_CHANGED, { data: null, error: e.error });

[dsilhavy]

@ed0wolf can you address my comment?

[dsilhavy]

@ed0wolf Thanks for the changes.

Following our contribution guidelines, and since this seems to be your first PR, could you please send me a signed copy of dash.js feedback agreement?

[ed0wolf]

Apologies for the delay.

I was a bit confused why the other Events didn't have the correct error type, figured someone knew better.. 🤷

I looked through those events and fixed the the error type for the events which get emitted with DashJSError.

I also noticed that DashJSError doesn't extend Error this means err instanceof Error === false, which doesn't seem obvious to me.

Thanks!

[ed0wolf]

@dsilhavy Where should I email the Feedback Agreement?

[dsilhavy]

Via email is fine: edit