Moved DISABLE_LOGIN check to getServerSideProps.

pages/login.js

@@ -2,8 +2,8 @@ import React from 'react';
 import Layout from 'components/layout/Layout';
 import LoginForm from 'components/forms/LoginForm';
 
-export default function LoginPage() {
-  if (process.env.loginDisabled) {
+export default function LoginPage({ loginDisabled }) {
+  if (loginDisabled) {
     return null;
   }
 
@@ -13,3 +13,9 @@ export default function LoginPage() {
     </Layout>
   );
 }
+
+export async function getServerSideProps() {
+  return {
+    props: { loginDisabled: !!process.env.DISABLE_LOGIN },
+  };
+}