Handle data received from server (#187)

@@ -140,8 +140,11 @@ sealed class RoomEvent(val room: Room) : Event() {
 
     /**
      * Received data published by another participant
+     *
+     * @param data the published data
+     * @param participant the participant if available
      */
-    class DataReceived(room: Room, val data: ByteArray, val participant: RemoteParticipant) : RoomEvent(room)
+    class DataReceived(room: Room, val data: ByteArray, val participant: RemoteParticipant?) : RoomEvent(room)
 
     /**
      * The connection quality for a participant has changed.

@@ -699,12 +699,12 @@ constructor(
      * @suppress
      */
     override fun onUserPacket(packet: LivekitModels.UserPacket, kind: LivekitModels.DataPacket.Kind) {
-        val participant = remoteParticipants[packet.participantSid] ?: return
+        val participant = remoteParticipants[packet.participantSid]
         val data = packet.payload.toByteArray()
 
         listener?.onDataReceived(data, participant, this)
         eventBus.postEvent(RoomEvent.DataReceived(this, data, participant), coroutineScope)
-        participant.onDataReceived(data)
+        participant?.onDataReceived(data)
     }
 
     /**
@@ -1027,7 +1027,7 @@ interface RoomListener {
     /**
      * Received data published by another participant
      */
-    fun onDataReceived(data: ByteArray, participant: RemoteParticipant, room: Room) {}
+    fun onDataReceived(data: ByteArray, participant: RemoteParticipant?, room: Room) {}
 
     /**
      * The connection quality for a participant has changed.

@@ -108,7 +108,7 @@ class CallViewModel(
                     when (it) {
                         is RoomEvent.FailedToConnect -> mutableError.value = it.error
                         is RoomEvent.DataReceived -> {
-                            val identity = it.participant.identity ?: ""
+                            val identity = it.participant?.identity ?: "server"
                             val message = it.data.toString(Charsets.UTF_8)
                             mutableDataReceived.emit("$identity: $message")
                         }