title: Two windows appear instead of one
body: <p>Every time I start this application two windows appear. I don't really see the problem there:</p>
  
  <pre><code>class GUI(pyglet.window.Window):
  def __init__(self):
      super(GUI, self).__init__()
      self.initUI()
  
  def initUI(self):
      self.window = pyglet.window.Window()
  
  
  @window.event
  def on_draw(self):
      self.window.clear()
      pyglet.graphics.draw(2, pyglet.gl.GL_POINTS,('v2i',(10,15, 50, 50)))
  </code></pre>