Crash when stopping stream (KVO)

[squarefrog]

I've seen a few of these crashes:

Fatal Exception: NSRangeException Cannot remove an observer <ORGMEngine 0x170283430> for the key path "endOfInput" from <ORGMInputUnit 0x1700927f0> because it is not registered as an observer.

The crash points to this line.

This is similar to issue #58, but it is important to note that it is a separate crash.

[diogobalseiro]

+1