Removing event listener in event handler causes other handlers to not always fire

Created by: justinanastos

Steps to reproduce

1. Attach two event handlers to listen to a single event using mediaPlayer.on()
2. In the first event handler, call mediaPlayer.off() to remove the handler being responded to
3. The second event will not fire

Observed behaviour

I expect all event handlers to fire, but they will not.

Reason

The cause is found here:

https://github.com/Dash-Industry-Forum/dash.js/blob/development/src/core/EventBus.js#L75

handlers[type] = handlers[type].splice(idx, 1);

interacting with

https://github.com/Dash-Industry-Forum/dash.js/blob/development/src/core/EventBus.js#L87

handlers[type].forEach( handler => handler.callback.call(handler.scope, payload) );

The handlers[type] array is mutated in place and short-circuits the handlers[type].forEach() loop. If I change the off() behavior the following:

handlers[type] = handlers[type].slice(0).splice(idx, 1);

The original array is not mutated and all handlers will fire as expected.