fix RTCPeerConnection.prototype.addTrack by adding MediaStream if not…

… available and prevent webrtc-adapter to overide getLocalStreams with bad SHAM

js/RTCPeerConnection.js

@@ -48,6 +48,7 @@ function RTCPeerConnection(pcConfig, pcConstraints) {
 	// Fix webrtc-adapter bad SHIM on addTrack causing error when original does support multiple streams.
 	// NotSupportedError: The adapter.js addTrack polyfill only supports a single stream which is associated with the specified track.
 	Object.defineProperty(this, 'addTrack', RTCPeerConnection.prototype_descriptor.addTrack);
+	Object.defineProperty(this, 'getLocalStreams', RTCPeerConnection.prototype_descriptor.getLocalStreams);
 
 	// Public atributes.
 	this._localDescription = null;
@@ -419,6 +420,8 @@ RTCPeerConnection.prototype.addTrack = function (track, stream) {
 	}
 
 	// Add localStreams if missing
+	stream = stream || Object.values(this.localStreams)[0] || new MediaStream();
+
 	// Fix webrtc-adapter bad SHIM on addStream
 	if (stream) {
 		if (!(stream instanceof MediaStream.originalMediaStream)) {