fix(Locomotion): correctly set other touchpad control enable state

There was an issue where if the touchpad was being held down when the
scene started and then released, the other touchpad control enable
state was being set to disabled because the touchpad axis change
hadn't occurred therefore the previous object control state was
always being set to false.

Assets/VRTK/Source/Scripts/Locomotion/VRTK_TouchpadControl.cs

@@ -37,11 +37,13 @@ public class VRTK_TouchpadControl : VRTK_ObjectControl
 
         protected bool touchpadFirstChange;
         protected bool otherTouchpadControlEnabledState;
+        protected bool otherTouchpadControlEnabledStateSet;
 
         protected override void OnEnable()
         {
             base.OnEnable();
             touchpadFirstChange = true;
+            otherTouchpadControlEnabledStateSet = false;
         }
 
         protected override void ControlFixedUpdate()
@@ -112,9 +114,10 @@ protected virtual bool TouchpadTouched()
 
         protected virtual void TouchpadAxisChanged(object sender, ControllerInteractionEventArgs e)
         {
-            if (touchpadFirstChange && otherObjectControl && disableOtherControlsOnActive && e.touchpadAxis != Vector2.zero)
+            if (touchpadFirstChange && otherObjectControl != null && disableOtherControlsOnActive && e.touchpadAxis != Vector2.zero)
             {
                 otherTouchpadControlEnabledState = otherObjectControl.enabled;
+                otherTouchpadControlEnabledStateSet = true;
                 otherObjectControl.enabled = false;
             }
             currentAxis = (ValidPrimaryButton() ? e.touchpadAxis : Vector2.zero);
@@ -127,7 +130,7 @@ protected virtual void TouchpadAxisChanged(object sender, ControllerInteractionE
 
         protected virtual void TouchpadTouchEnd(object sender, ControllerInteractionEventArgs e)
         {
-            if (otherObjectControl && disableOtherControlsOnActive)
+            if (otherTouchpadControlEnabledStateSet && otherObjectControl != null && disableOtherControlsOnActive)
             {
                 otherObjectControl.enabled = otherTouchpadControlEnabledState;
             }