RTCView should support null stream

[wilkinsonj]

Describe the bug

The native RTCView can be provided a streamURL of null, for example streamUrl={localStream?.toURL()}

However, the RTCView in this library throws an error if localStream is null, for example stream={localStream}

It would be better if stream had the same logic behind the scenes

[8BallBomBom]

Understandable, there are a few things which definitely need pulling into line.
Will put this on the list for the next major update 🤔