Postgis error: TypeError: 'NoneType' object has no attribute '__getitem__'

[rotsee]

I constantly get the error TypeError: 'NoneType' object has no attribute '__getitem__' when using a postgis table as a layer source. Any ideas on how to troubleshoot? Here is traceback:

 File "createMap2.py", line 201, in <module>
   K.generate(config, outfile=fullfilename)
 File "/usr/local/lib/python2.7/dist-packages/kartograph.py-0.6.8-py2.7.egg/kartograph/kartograph.py", line 46, in generate
   _map = Map(opts, self.layerCache, format=format)
  File "/usr/local/lib/python2.7/dist-packages/kartograph.py-0.6.8-py2.7.egg/kartograph/map.py", line 42, in __init__
   layer = MapLayer(layer_id, layer_cfg, me, layerCache)
 File "/usr/local/lib/python2.7/dist-packages/kartograph.py-0.6.8-py2.7.egg/kartograph/maplayer.py", line 35, in __init__
 self.source = handle_layer_source(self.options, self.cache)
 File "/usr/local/lib/python2.7/dist-packages/kartograph.py-0.6.8-py2.7.egg/kartograph/layersource/__init__.py", line 49, in handle_layer_source
   src = PostGISLayer(src[8:], query=layer['query'], table=layer['table'])
 File "/usr/local/lib/python2.7/dist-packages/kartograph.py-0.6.8-py2.7.egg/kartograph/layersource/postgislayer.py", line 39, in __init__
   self.geom_col = cur.fetchone()[0]

TypeError: 'NoneType' object has no attribute 'getitem'