fix(auth): update admin check to safely access user property

- Modified the admin check to use optional chaining, ensuring that the user property is accessed only if it exists, preventing potential runtime errors.

packages/server/src/lib/auth.ts

@@ -42,7 +42,7 @@ const { handler, api } = betterAuth({
 				},
 			});
 
-			if (admin) {
+			if (admin?.user) {
 				return [
 					...(admin.user.serverIp
 						? [`http://${admin.user.serverIp}:3000`]