rtsp: fix crash when setupping tracks between stream changes (#5253) (#5257)

Author: aler9

internal/servers/rtsp/session.go

@@ -194,6 +194,13 @@ func (s *session) onAnnounce(c *conn, ctx *gortsplib.ServerHandlerOnAnnounceCtx)
 	}, nil
 }
 
+func (s *session) rtspStream() *gortsplib.ServerStream {
+	if !s.isTLS {
+		return s.stream.RTSPStream(s.rserver)
+	}
+	return s.stream.RTSPSStream(s.rserver)
+}
+
 // onSetup is called by rtspServer.
 func (s *session) onSetup(c *conn, ctx *gortsplib.ServerHandlerOnSetupCtx,
 ) (*base.Response, *gortsplib.ServerStream, error) {
@@ -226,7 +233,7 @@ func (s *session) onSetup(c *conn, ctx *gortsplib.ServerHandlerOnSetupCtx,
 	}
 
 	switch s.rsession.State() {
-	case gortsplib.ServerSessionStateInitial, gortsplib.ServerSessionStatePrePlay: // play
+	case gortsplib.ServerSessionStateInitial: // play
 		path, stream, err := s.pathManager.AddReader(defs.PathAddReaderReq{
 			Author: s,
 			AccessRequest: defs.PathAccessRequest{
@@ -261,16 +268,14 @@ func (s *session) onSetup(c *conn, ctx *gortsplib.ServerHandlerOnSetupCtx,
 		s.path = path
 		s.stream = stream
 
-		var rstream *gortsplib.ServerStream
-		if !s.isTLS {
-			rstream = stream.RTSPStream(s.rserver)
-		} else {
-			rstream = stream.RTSPSStream(s.rserver)
-		}
+		return &base.Response{
+			StatusCode: base.StatusOK,
+		}, s.rtspStream(), nil
 
+	case gortsplib.ServerSessionStatePrePlay: // play, subsequent calls
 		return &base.Response{
 			StatusCode: base.StatusOK,
-		}, rstream, nil
+		}, s.rtspStream(), nil
 
 	default: // record
 		return &base.Response{