listenersMatching now also returns matching wildcard subscriptions
Not throwing if there are no listeners
Emitting error events

If an error occures in 'emit' because one of the callbacks throws an
exception or a callback is invoked with an error, the following rules apply:

- If any error handlers exist in the namespace of the emitted event,
  they are invoked with the error as the only argument.
- If there was no error handlerr in the namespace, but there is a global
  'error' event listener, that listener is invoked with the error as the
  only argument.
- If no error handlers exist, the error is thrown.

In case of an exception thrown by one of the error handlers, all other
error handlers will still be invoked and the error is rethrown afterwards.
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