Avoid null attribute values (in case of strict DB settings).

module/VuFind/src/VuFind/Auth/LDAP.php

@@ -280,7 +280,7 @@ class LDAP extends AbstractBase
                         $value = $data[$i][$configValue][0];
                         $this->debug("found $field = $value");
                         if ($field != "cat_password") {
-                            $user->$field = $value;
+                            $user->$field = ($value === null) ? '' : $value;
                         } else {
                             $catPassword = $value;
                         }

module/VuFind/src/VuFind/Auth/Shibboleth.php

@@ -114,7 +114,7 @@ class Shibboleth extends AbstractBase
             if (isset($shib->$attribute)) {
                 $value = $request->getServer()->get($shib->$attribute);
                 if ($attribute != 'cat_password') {
-                    $user->$attribute = $value;
+                    $user->$attribute = ($value === null) ? '' : $value;
                 } else {
                     $catPassword = $value;
                 }