server: fix crash in case of requests with nil URL (#458)

---------

Co-authored-by: aler9 <46489434+aler9@users.noreply.github.com>

server_conn.go

@@ -208,10 +208,15 @@ func (sc *ServerConn) handleRequestInner(req *base.Request) (*base.Response, err
 	if cseq, ok := req.Header["CSeq"]; !ok || len(cseq) != 1 {
 		return &base.Response{
 			StatusCode: base.StatusBadRequest,
-			Header:     base.Header{},
 		}, liberrors.ErrServerCSeqMissing{}
 	}
 
+	if req.Method != base.Options && req.URL == nil {
+		return &base.Response{
+			StatusCode: base.StatusBadRequest,
+		}, liberrors.ErrServerInvalidPath{}
+	}
+
 	sxID := getSessionID(req.Header)
 
 	var path string

server_test.go

@@ -311,7 +311,40 @@ func TestServerErrorCSeqMissing(t *testing.T) {
 	res, err := writeReqReadRes(conn, base.Request{
 		Method: base.Options,
 		URL:    mustParseURL("rtsp://localhost:8554/"),
-		Header: base.Header{},
+	})
+	require.NoError(t, err)
+	require.Equal(t, base.StatusBadRequest, res.StatusCode)
+
+	<-nconnClosed
+}
+
+func TestServerErrorNilURL(t *testing.T) {
+	nconnClosed := make(chan struct{})
+
+	s := &Server{
+		Handler: &testServerHandler{
+			onConnClose: func(ctx *ServerHandlerOnConnCloseCtx) {
+				require.EqualError(t, ctx.Error, "invalid path")
+				close(nconnClosed)
+			},
+		},
+		RTSPAddress: "localhost:8554",
+	}
+	err := s.Start()
+	require.NoError(t, err)
+	defer s.Close()
+
+	nconn, err := net.Dial("tcp", "localhost:8554")
+	require.NoError(t, err)
+	defer nconn.Close()
+	conn := conn.NewConn(nconn)
+
+	res, err := writeReqReadRes(conn, base.Request{
+		Method: base.Describe,
+		URL:    nil,
+		Header: base.Header{
+			"CSeq": base.HeaderValue{"1"},
+		},
 	})
 	require.NoError(t, err)
 	require.Equal(t, base.StatusBadRequest, res.StatusCode)