Fixed some null refs with mouse pointer

Author: StephenHodgson

Assets/MixedRealityToolkit-SDK/Features/UX/Scripts/Pointers/MousePointer.cs

@@ -144,7 +144,7 @@ public override void OnSourcePoseChanged(SourcePoseEventData<Vector2> eventData)
         /// <inheritdoc />
         public override void OnInputDown(InputEventData eventData)
         {
-            cursorWasDisabledOnDown = !BaseCursor.IsVisible;
+            cursorWasDisabledOnDown = isDisabled;
 
             if (cursorWasDisabledOnDown)
             {
@@ -160,7 +160,7 @@ public override void OnInputDown(InputEventData eventData)
         /// <inheritdoc />
         public override void OnInputUp(InputEventData eventData)
         {
-            if (BaseCursor.IsVisible && !cursorWasDisabledOnDown)
+            if (!isDisabled && !cursorWasDisabledOnDown)
             {
                 base.OnInputUp(eventData);
             }
@@ -230,14 +230,15 @@ private void UpdateMousePosition(float mouseX, float mouseY)
                     BaseCursor?.SetVisibility(true);
                     transform.rotation = CameraCache.Main.transform.rotation;
                 }
-                else
-                {
-                    timeoutTimer = 0.0f;
-                }
 
                 isDisabled = false;
             }
 
+            if (!isDisabled)
+            {
+                timeoutTimer = 0.0f;
+            }
+
             var newRotation = Vector3.zero;
             newRotation.x += mouseX;
             newRotation.y += mouseY;