<!--THE CONDITIONAL SIDEBAR CONTENTS-->
<?php if(get_field('alternate_sidebar_content')) {?>
<?php the_field('alternate_sidebar_content'); ?>
<?php } ?><!-- ends the first condition -->
<?php if(!get_field('alternate_sidebar_content')) {?>
<?php if ( ! dynamic_sidebar( 'sidebar-3' ) ) : ?>
<?php endif; // end sidebar widget area ?>
<?php }?> <!-- ends the second outer condition -->

