Merge pull request #36 from QGEP/fix_error_on_null_point

Do not raise exception on null geometries

src/tools/qgepnetwork.py

@@ -123,7 +123,7 @@ def _addVertices(self):
 
             try:
                 vertex = feat.geometry().asPoint()
-            except AttributeError:
+            except ValueError:
                 # TODO Add to problem log
                 pass
             self.graph.add_node(fid, point=vertex, objType=obj_type, objId=obj_id)