handle case where box is not activated

src/mailer.js

@@ -1,5 +1,3 @@
-/* jslint node: true */
-
 'use strict';
 
 exports = module.exports = {
@@ -200,6 +198,8 @@ function getAdminEmails(callback) {
     users.getAllAdmins(function (error, admins) {
         if (error) return callback(error);
 
+        if (admins.length === 0) return callback(new Error('No admins on this cloudron')); // box not activated yet
+
         var adminEmails = [ ];
         admins.forEach(function (admin) { adminEmails.push(admin.email); });