Better fix for null dereferencing issue. Fix initial Color sensor mode (default).

sim/state/color.ts

@@ -3,12 +3,13 @@
 namespace pxsim {
 
     export enum ColorSensorMode {
+        None = -1,
         Reflected = 0,
         Ambient = 1,
         Colors = 2,
         RefRaw = 3,
         RgbRaw = 4,
-        ColorCal = 5
+        ColorCal = 5,
     }
 
     export enum ThresholdState {
@@ -24,6 +25,7 @@ namespace pxsim {
 
         constructor(port: number) {
             super(port);
+            this.mode = -1;
         }
 
         getDeviceType() {