Steps to reproduce the issue

Edit an article.
View page source.
Search for class="".

Expected result

No empty class output.

Actual result

<div class="control-group">
			<div class="control-label"><label id="jform_modified_by-lbl" for="jform_modified_by" class="">
	Modified By</label>
</div>

Additional comments

Custom fields are affected by this too.

I attempted to fix this in \joomla-cms-staging\layouts\joomla\form\renderfield.php, however, I am unable to find out where $label is generated.

<div class="control-group<?php echo $class; ?>"<?php echo $rel; ?>>
	<?php if (empty($options['hiddenLabel'])) : ?>
		<div class="control-label"><?php echo $label; ?></div>
	<?php endif; ?>
	<div class="controls"><?php echo $input; ?></div>
</div>