Fixed share token check.

lib/middleware.js

@@ -29,12 +29,12 @@ export const useAuth = createMiddleware(async (req, res, next) => {
   const payload = parseSecureToken(token, secret());
   const shareToken = await parseShareToken(req);
 
-  let user;
+  let user = null;
   const { userId, key } = payload || {};
 
   if (validate(userId)) {
     user = await getUser({ id: userId });
-  } else if (redis.enabled) {
+  } else if (redis.enabled && key) {
     user = await redis.get(key);
   }