diff --git a/lib/pear/HTML/QuickForm/hierselect.php b/lib/pear/HTML/QuickForm/hierselect.php
index 1bce43b6e7a..89376a27644 100644
--- a/lib/pear/HTML/QuickForm/hierselect.php
+++ b/lib/pear/HTML/QuickForm/hierselect.php
@@ -496,7 +496,7 @@ JAVASCRIPT;
             $ret = parent::onQuickFormEvent($event, $arg, $caller);
             // add onreset handler to form to properly reset hierselect (see bug #2970)
             if ('addElement' == $event) {
-                $onReset = $caller->getAttribute('onreset');
+                $onReset = $caller->getAttribute('onreset') ?? '';
                 if (strlen($onReset)) {
                     if (strpos($onReset, '_hs_setupOnReset')) {
                         $caller->updateAttributes(array('onreset' => str_replace('_hs_setupOnReset(this, [', "_hs_setupOnReset(this, ['" . $this->_escapeString($this->getName()) . "', ", $onReset)));
diff --git a/lib/pear/readme_moodle.txt b/lib/pear/readme_moodle.txt
index ff0ab2da5d2..9c10c9ffbd6 100644
--- a/lib/pear/readme_moodle.txt
+++ b/lib/pear/readme_moodle.txt
@@ -32,7 +32,7 @@ MDL-70457 - PHP 7.4 curly brackets string access fix.
 MDL-71126 - Quiz: Manual grading page size preference can get stuck at 0
             Including in this change:
              - New positiveint regex rule to check if the value is a positive integer
-MDL-76102 / MDL-77081
+MDL-76102 / MDL-77081 / MDL-83835
             PHP 8.1 passing null to a non-nullable argument of a built-in function is deprecated
 MDL-77164 - PHPdocs corrections
 MDL-78145 - PHP 8.2 compliance. Added a missing class property that still need to be declared