title: Blender render " location: <unknown location> and " UnboundLocalError " with Pov Ray addon
body: <p>I am not sure this is the best place the ask but here I go...</p>
  
  <p>I am trying to render an image with the Pov ray addon for Blender 2.79b. When I do so, it just shows me an ugly checkerboard. </p>
  
  <p>After some goofing around I clicked the info tab and it showed me this little message:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Program Files\Blender Foundation\Blender\2.79\scripts\addons\render_povray\render.py", line 4147, in render
      self._export(scene, povPath, renderImagePath)
    File "C:\Program Files\Blender Foundation\Blender\2.79\scripts\addons\render_povray\render.py", line 3837, in _export
      write_pov(self._temp_file_in, scene, info_callback)
    File "C:\Program Files\Blender Foundation\Blender\2.79\scripts\addons\render_povray\render.py", line 3648, in write_pov
      shading.writeMaterial(using_uberpov, DEF_MAT_NAME, scene, tabWrite, safety, comments, uniqueName, materialNames, material)
    File "C:\Program Files\Blender Foundation\Blender\2.79\scripts\addons\render_povray\shading.py", line 251, in writeMaterial
      if(t and t.use and validPath and
  UnboundLocalError: local variable 'validPath' referenced before assignment
  
  location: &lt;unknown location&gt;:-1
  </code></pre>
  
  <p>I don't really understand Python (or coding in general) unfortunately, so I don't want to touch anything until I understand it better.   </p>