@Override
    protected void removeSpatialData(Spatial spat) {
        rigidBody.setUserObject(null);
    }
Destroy spatial-dependent data. Invoked when this control is removed from
a spatial.

@param spat the previously controlled spatial (not null)
jme3-jbullet/src/main/java/com/jme3/bullet/control/BetterCharacterControl.java