Refactor app.js maintenance mode check to use guard clause

Co-authored-by: cubap <1119165+cubap@users.noreply.github.com>

Author: Copilot

app.js

@@ -72,10 +72,9 @@ app.use(express.static(path.join(__dirname, 'public')))
 app.all('*', (req, res, next) => {
   if(process.env.DOWN === "true"){
       res.status(503).json({"message":"RERUM v1 is down for updates or maintenance at this time.  We apologize for the inconvenience.  Try again later."})
+      return
   }
-  else{
-      next() //pass on to the next app.use
-  }
+  next() //pass on to the next app.use
 })
 
 app.use('/', indexRouter)