Update 'locallib.php'

Synchronizing iAssign Git with the current iAssign stable version (until Moodle 5.0).
Small changes in: ilm_manager_form.php, ilm_manager.php, lang/*/iassign.php
Bigger changes in: lib.php, settings_form.php, settings.php, version.php, backup/moodle2/*.php, ilm_debug/escreva.php, ilm_handlers/java.php
New iLM versions: iassign/ilm/iFractions/, iassign/ilm/iHanoi/, iassign/ilm/iVProg/
New file (was missing): settings_activities.php

locallib.php

@@ -9729,7 +9729,7 @@ class iassign_language {
   //  @return string Return as string with xml tags
   static function json_to_xml ($json) {
     $xml = "";
-   $json = json_decode($json);
+    $json = json_decode($json);
     foreach ($json as $key => $value) {
       $xml .= "\n    <" . $key . ">" . $value . "</" . $key . ">";
       }