serve: Fix a bug where empty route metadata is not the same as invalid route. Some routes can capture no metadata at all, like for example when `foo/%path:slug%` is capturing URL `foo`. The route is still valid, so it returns an empty dictionary. It's not the same as returning `None`, which means "no match".

@echo off
setlocal

set CUR_DIR=%~dp0
set CHEF=%CUR_DIR%..\bin\chef
set OUT_DIR=%CUR_DIR%..\piecrust\resources\messages
set ROOT_DIR=%CUR_DIR%messages

%CHEF% --root=%ROOT_DIR% bake -o %OUT_DIR%
del %OUT_DIR%\index.html