There is an error in line 9 of header_layout_transparent.php
It has an echo in the middle of the string concatenation
<header id="ABdev_main_header" class="clearfix transparent <?php echo esc_attr($sticky_header_class) .' '. echo($switch_header_class); ?>">
It should be:
<header id="ABdev_main_header" class="clearfix transparent <?php echo esc_attr($sticky_header_class) .' '.$switch_header_class; ?>">
