Fix RtpReceiver use after free on Android platform (#165)

Author: alexlapa

CHANGELOG.md

@@ -33,6 +33,7 @@ All user visible changes to this project will be documented in this file. This p
 - Unexpected audio category on `setOutputAudioId` call on [iOS]. ([#146])
 - Race condition bug on `setOutputAudioId` call on [Android]. ([#146])
 - Race condition bug on input/output device switch on desktop platforms. ([#151])
+- `RtpReceiver` use after free on [Android]. ([#165])
 
 [#137]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/137
 [#139]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/139
@@ -47,6 +48,7 @@ All user visible changes to this project will be documented in this file. This p
 [#156]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/156
 [#162]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/162
 [#164]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/164
+[#165]: https://github.com/instrumentisto/medea-flutter-webrtc/pull/165
 [`dart:html`]: https://dart.dev/libraries/dart-html
 [`package:web`]: https://pub.dev/packages/web
 [126.0.6478.182-r2]: https://github.com/instrumentisto/libwebrtc-bin/releases/tag/126.0.6478.182-r2

android/src/main/kotlin/com/instrumentisto/medea_flutter_webrtc/proxy/PeerObserver.kt

@@ -65,11 +65,11 @@ class PeerObserver : PeerConnection.Observer {
   override fun onTrack(transceiver: RtpTransceiver?) {
     if (transceiver != null && peer != null) {
       if (!peer!!.disposed) {
+        val receiverId = transceiver.receiver.id()
         Handler(Looper.getMainLooper()).post {
-          val receiver = transceiver.receiver
           val transceivers = peer?.getTransceivers()!!
           for (trans in transceivers) {
-            if (trans.receiver.id == receiver.id()) {
+            if (trans.receiver.id == receiverId) {
               peer?.observableEventBroadcaster()?.onTrack(trans.receiver.track, trans)
             }
           }