message: Initialize DisplayHelper when using textureView in ModelViewer
diff: @@ -141,6 +141,7 @@ class ModelViewer(val engine: Engine) : android.view.View.OnTouchListener {
  this.textureView = textureView
  gestureDetector = GestureDetector(textureView, cameraManipulator)
  + displayHelper = DisplayHelper(textureView.context)
  uiHelper.renderCallback = SurfaceCallback()
  uiHelper.attachTo(textureView)
  addDetachListener(textureView)
  