Fix error when uploading through legacy selector without metadata

mod_form.php

@@ -367,7 +367,11 @@ class mod_hvp_mod_form extends moodleform_mod {
         unset($data->h5pparams);
 
         if ($data->h5paction === 'upload') {
-            if (empty($data->metadata) || empty($data->metadata->title)) {
+            if (empty($data->metadata)) {
+                $data->metadata = new stdClass();
+            }
+
+            if (empty($data->metadata->title)) {
                 // Fix for legacy content upload to work.
                 // Fetch title from h5p.json or use a default string if not available.
                 $h5pvalidator = \mod_hvp\framework::instance('validator');