removed dead code

python/tools/audiobook/catalog.py

@@ -169,7 +169,6 @@ def csv_id(row: dict[str, str | None], csv_path: Path, row_number: int) -> int |
     except ValueError as error:
         msg = f"{csv_path}:{row_number}: id must be an integer: {value}"
         raise CatalogImportError(msg) from error
-    return None
 
 
 if __name__ == "__main__":