Fixed config issue with dem (#339)

            else:

                boundary = generate_boundary(self.geodata.raster_size[::-1])  # yx to xy

                try:

                    geodata = GeoDataset(spatial.get('dem'))

                    geodata = GeoDataset(config['spatial']['dem'])

                except Exception as e:

                    warnings.warn('Unable to get the Geodata from dem.\n{}'.format(e))

                    geodata = 0.0