conference: check for nil rtp tracks

Author: daniel-abramov

pkg/conference/processor.go

@@ -140,6 +140,10 @@ func (c *Conference) handleDataChannelMessage(participant *Participant, sfuMessa
 
 		// Get the tracks that correspond to the tracks that the participant wants to receive.
 		for _, track := range c.getTracks(sfuMessage.Start) {
+			if track == nil {
+				participant.logger.Errorf("Bug, track is nil")
+			}
+
 			if err := participant.peer.SubscribeTo(track); err != nil {
 				participant.logger.Errorf("Failed to subscribe to track: %v", err)
 				return

pkg/conference/state.go

@@ -79,7 +79,7 @@ func (c *Conference) getAvailableStreamsFor(forParticipant ParticipantID) event.
 
 // Helper that returns the list of streams inside this conference that match the given stream IDs.
 func (c *Conference) getTracks(identifiers []event.SFUTrackDescription) []*webrtc.TrackLocalStaticRTP {
-	tracks := make([]*webrtc.TrackLocalStaticRTP, len(identifiers))
+	tracks := make([]*webrtc.TrackLocalStaticRTP, 0)
 	for _, participant := range c.participants {
 		// Check if this participant has any of the tracks that we're looking for.
 		for _, identifier := range identifiers {