Initialize the variable n_cols_added (#136)

src/dbt_osmosis/core/osmosis.py

@@ -1059,6 +1059,7 @@ def update_schema_file_and_node(
     ) -> Tuple[int, int, int, int]:
         """Take action on a schema file mirroring changes in the node."""
         logger().info(":microscope: Looking for actions for %s", node.unique_id)
+        n_cols_added = 0
         if not self.skip_add_columns:
             n_cols_added = self.add_missing_cols_to_node_and_model(
                 missing_columns, node, section, columns_db_meta