Fix Postgres support

as far as I can tell

src/api/controllers/BaseController.php

@@ -81,8 +81,8 @@ abstract class BaseController {
   protected function getAdminEmailAddresses($boardId) {
     $emails = R::getAll('SELECT email FROM user u ' .
       'JOIN board_user bu ON u.id = bu.user_id ' .
-      'WHERE u.security_level < 3 AND u.email <> "" AND board_id = ?',
-      [$boardId]);
+      'WHERE u.security_level < 3 AND u.email <> ? AND board_id = ?',
+      ['', $boardId]);
 
     return count($emails) > 0 ? $emails[0] : [];
   }