fix: Return Disconnected room ConnectionState if engine is nil

- With the refactoring of reading the connection state directly from the engine there the non-exposed disconnected engine cannot be guarded and will panic: return disconnected if the engine is nil

Author: Marius Gassen

room.go

@@ -536,6 +536,10 @@ func (r *Room) ConnectionState() ConnectionState {
 	r.lock.RLock()
 	defer r.lock.RUnlock()
 
+	if r.engine == nil {
+		return ConnectionStateDisconnected
+	}
+
 	switch r.engine.currentState() {
 	case connectionManagerStateInitial, connectionManagerStateClosed:
 		return ConnectionStateDisconnected

room_test.go

@@ -116,3 +116,8 @@ func TestOnRoomUpdateDeliversLateSID(t *testing.T) {
 		return room.SID() == "RM_late"
 	}, time.Second, 10*time.Millisecond, "SID() never returned the SID delivered via OnRoomUpdate")
 }
+
+func TestConnectionStateWithoutEngine(t *testing.T) {
+	room := NewRoom(nil)
+	require.Equal(t, ConnectionStateDisconnected, room.ConnectionState())
+}