[4.0] Fix form validation error (#34513)

* Fix form validation error

* Thanks :)

Co-authored-by: Dimitris Grammatikogiannis <[email protected]>

* Fix typo

Co-authored-by: Dimitris Grammatikogiannis <[email protected]>

Author: joomdonation

build/media_source/system/js/fields/validate.es6.js

@@ -117,11 +117,11 @@ class JFormValidator {
       const elMsg = document.createElement('span');
       elMsg.classList.add('form-control-feedback');
       if (empty && empty === 'checkbox') {
-        elMsg.innerHTML = Joomla.sanitizeHtml(message) || Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_REQUIRED_CHECK'));
+        elMsg.innerHTML = message !== null ? Joomla.sanitizeHtml(message) : Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_REQUIRED_CHECK'));
       } else if (empty && empty === 'value') {
-        elMsg.innerHTML = Joomla.sanitizeHtml(message) || Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_REQUIRED_VALUE'));
+        elMsg.innerHTML = message !== null ? Joomla.sanitizeHtml(message) : Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_REQUIRED_VALUE'));
       } else {
-        elMsg.innerHTML = Joomla.sanitizeHtml(message) || Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_INVALID_VALUE'));
+        elMsg.innerHTML = message !== null ? Joomla.sanitizeHtml(message) : Joomla.sanitizeHtml(Joomla.Text._('JLIB_FORM_FIELD_INVALID_VALUE'));
       }
 
       if (label) {