Bug 1773043: Check for logoxs object param

This can be missing in collection object when upgrading from older
site and new db field is not created yet

behatnotneeded

Change-Id: I275a6387546eb8adaefd8b35f8b96dc754979cf5
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>

htdocs/auth/user.php

@@ -921,7 +921,7 @@ class User {
         if (!is_null($themeinstitution)) {
             $themename  = $institutions[$themeinstitution]->theme;
             $headerlogo = $institutions[$themeinstitution]->logo;
-            $headerlogosmall = $institutions[$themeinstitution]->logoxs;
+            $headerlogosmall = isset($institutions[$themeinstitution]->logoxs) ? $institutions[$themeinstitution]->logoxs : null;
             if ($institutions[$themeinstitution]->style) {
                 $stylesheet = get_config('wwwroot') . 'style.php?id=' . $institutions[$themeinstitution]->style;
                 if ($nocachecss) {