quicktag_empty_link

// Add Quicktags
function empty_link() {

	if ( wp_script_is( 'quicktags' ) ) {
	?>
	<script type="text/javascript">
	QTags.addButton( '', '', '<a href="" title="" target="">', '</a>', '', '', 11 );
	</script>
	<?php
	}

}

// Hook into the 'admin_print_footer_scripts' action
add_action( 'admin_print_footer_scripts', 'empty_link' );