Fix code -- we have a dict not a Shape object.

Author: dbrnz

mapmaker/flatmap/__init__.py

@@ -292,7 +292,7 @@ def new_feature(self, layer_id: str, geometry, properties, is_group=False) -> Op
     #===============================================================================================
         properties['layer'] = layer_id
         self.properties_store.update_properties(properties)   # Update from JSON properties file
-        if properties.id in self.__features_with_id:
+        if properties.get('id') in self.__features_with_id:
             log.error('Duplicate feature id', id=properties.id)
             return None
         self.__last_geojson_id += 1