Steps to reproduce the issue

Display Contacts Manager or select a contact and use batch

Expected result

The Option No User is proposed when editing a contact or in the batch modal.

Actual result

PHP Notice: Undefined variable: noUser in /layouts/joomla/html/batch/user.php on line 26

I tried to modify both in
/administrator/components/com_contact/tmpl/contacts/default_batch_body.php
and
/administrator/components/com_contact/tmpl/contacts/default_batch.php
the line
<?php echo LayoutHelper::render('joomla.html.batch.user', []); ?>
to
<?php echo LayoutHelper::render('joomla.html.batch.user', ['noUser => $noUser]); ?>
without success.

Then I found out that
<?php echo LayoutHelper::render('joomla.html.batch.user', []); ?>

is only used for contacts.

Therefore I modified //layouts/joomla/html/batch/user.php and commented out $noUser
to

//if ($noUser)
//{
	$optionNo = '<option value="0">' . Text::_('JLIB_HTML_BATCH_USER_NOUSER') . '</option>';
//}
?>
<label id="batch-user-lbl" for="batch-user" class="modalTooltip" title="<?php
echo HTMLHelper::_('tooltipText', 'JLIB_HTML_BATCH_USER_LABEL', 'JLIB_HTML_BATCH_USER_LABEL_DESC'); ?>">
	<?php echo Text::_('JLIB_HTML_BATCH_USER_LABEL'); ?>
</label>
<select name="batch[user_id]" class="custom-select" id="batch-user-id">
	<option value=""><?php echo Text::_('JLIB_HTML_BATCH_USER_NOCHANGE'); ?></option>
	<?php echo $optionNo; ?>
	<?php echo HTMLHelper::_('select.options', HTMLHelper::_('user.userlist'), 'value', 'text'); ?>
</select>

This solves the issue, but this layout could be used by a 3pd who would not want the "No User" option and therefore would need to override the layout.

Any idea what should really be done?