Why is the sun added twice to a world file?

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When I have created a new world using the GUI and save this world as .world file then the sun is added twice. I found at the top of the world file:

 <light name='sun' type='directional'>
  <cast_shadows>1</cast_shadows>
  <pose frame=''>0 0 10 0 -0 0</pose>
  <diffuse>0.8 0.8 0.8 1</diffuse>
  <specular>0.1 0.1 0.1 1</specular>
  <attenuation>
    <range>1000</range>
    <constant>0.9</constant>
    <linear>0.01</linear>
    <quadratic>0.001</quadratic>
  </attenuation>
  <direction>-0.5 0.5 -1</direction>
</light>

and at the bottom of the file this:

<light name='sun'>
  <pose frame=''>0 0 10 0 -0 0</pose>
</light>

Why is the sun added twice?