Access violation calling GuiControl::getExtent()

// GuiReticleCtrl.h
// a tickable bitmap reticle with a "soft" floating zone
...
class GuiReticleCtrl : public GuiBitmapCtrl, public virtual ITickable
{
  ...
protected:
  virtual void interpolateTick(F32 delta);
  virtual void processTick();
  virtual void advanceTime(F21 timeDelta);

  Point2I mCenter;  // center of the screen
  U16 mRadius, mCushion;  // radius and cushioning factor of the floating zone

public:
  DECLARE_CONOBJECT(GuiReticleCtrl);
  GuiReticleCtrl();
  ...
};

// GuiReticleCtrl.cc
// a tickable bitmap reticle with a "soft" floating zone
...
GuiReticleCtrl::GuiReticleCtrl()
{
  mCenter = getRoot()->getExtent() / 2;  // this is where run-time problems come up
  mRadius = 100;  // this will later be exposed to the console as a $Pref
  mCushion = 10;  // this will later be exposed to the console as a $Pref
}
...

// guiControl.h
...
Class GuiControl : public SimGroup
{
  ...
public:
  ...
  const Point2I& getExtent() { return mBounds.extent; } ///< Returns the extents of the control
  ...
};

Quote:Unhandled exception at 0x009a68e7 in torqueDemo_DEBUG.exe:
0xC0000005: Access violation reading location 0x00000080.

GuiReticleCtrl::GuiReticleCtrl()
{
  //mCenter = getRoot()->getExtent() / 2;  // this is where run-time problems come up
  Point2I test = getRoot()->getExtent();
  mCenter.x = 400;
  mCenter.y = 300;
  mRadius = 100;  // this will later be exposed to the console as a $Pref
  mCushion = 10;  // this will later be exposed to the console as a $Pref
}
...