Post nav links always show but disabled when at first or last rather than hide

Solved :)

by copying the function to my child theme and adding an extra check to see if a post exists and if not putput dummy << >> links that dont click

I also had to add the taxonomy name in the single-portfolio.php and to tell it to keep in same category only

echo avia_post_nav(true,'case-studies');

if(!function_exists('avia_post_nav'))
{
	function avia_post_nav($same_category = false, $taxonomy = 'category')
	{
		global $wp_version;
	        $settings = array();
	        $settings['same_category'] = $same_category;
	        $settings['excluded_terms'] = '';
			$settings['wpversion'] = $wp_version;
        
		//dont display if a fullscreen slider is available since they overlap 
		if((class_exists('avia_sc_layerslider') && !empty(avia_sc_layerslider::$slide_count)) || 
			class_exists('avia_sc_slider_full') && !empty(avia_sc_slider_full::$slide_count) ) $settings['is_fullwidth'] = true;

		$settings['type'] = get_post_type();
		//if ($taxonomy) {
			//$settings['taxonomy'] = $taxonomy;
		//} else {
			$settings['taxonomy'] = ($settings['type'] == 'portfolio') ? 'portfolio_entries' : $taxonomy;
		//}

		if(!is_singular() || is_post_type_hierarchical($settings['type'])) $settings['is_hierarchical'] = true;
		if($settings['type'] === 'topic' || $settings['type'] === 'reply') $settings['is_bbpress'] = true;

	        $settings = apply_filters('avia_post_nav_settings', $settings);
	        if(!empty($settings['is_bbpress']) || !empty($settings['is_hierarchical']) || !empty($settings['is_fullwidth'])) return;
	
	        if(version_compare($settings['wpversion'], '3.8', '>=' ))
	        {
	            $entries['prev'] = get_previous_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	            $entries['next'] = get_next_post($settings['same_category'], $settings['excluded_terms'], $settings['taxonomy']);
	        }
	        else
	        {
	            $entries['prev'] = get_previous_post($settings['same_category']);
	            $entries['next'] = get_next_post($settings['same_category']);
	        }
	        
		$entries = apply_filters('avia_post_nav_entries', $entries, $settings);
        $output = "";

		foreach ($entries as $key => $entry)
		{
            if(empty($entry)) { // continue;
			
			//echo '<div class="disabled-post-nav">';
		//echo '<a class="avia-post-nav avia-post-next with-image" ><span class="entry-info-wrap"><span class="entry-info"><span class="entry-image"></span></span></a>';
		//echo '</div>';
			
			$output .= "<div class='disabled-post-nav'><a class='avia-post-nav avia-post-{$key} {$class}' >";
		    //$output .= "    <span class='label iconfont' ".av_icon_string($key)."></span>";
		    $output .= "    <span class='entry-info-wrap'>";
		    $output .= "        <span class='entry-info'><span class='entry-image'></span>";
		   // $tc1     = "            <span class='entry-title'>{$the_title}</span>";
if($image)  //$tc2     = "            <span class='entry-image'>{$image}</span>";
            //$output .= $key == 'prev' ?  $tc1.$tc2 : $tc2.$tc1;
            $output .= "        </span>";
            //$output .= "    </span>";
		    $output .= "</a></div>";
			
			} else {
			$the_title 	= isset($entry->av_custom_title) ? $entry->av_custom_title : avia_backend_truncate(get_the_title($entry->ID),75," ");
			$link 		= isset($entry->av_custom_link)  ? $entry->av_custom_link  : get_permalink($entry->ID);
			$image 		= isset($entry->av_custom_image) ? $entry->av_custom_image : get_the_post_thumbnail($entry->ID, 'thumbnail');
			
            $tc1   = $tc2 = "";
            $class = $image ? "with-image" : "without-image";

            $output .= "<a class='avia-post-nav avia-post-{$key} {$class}' href='{$link}' >";//.$same_category.$taxonomy;
		    $output .= "    <span class='label iconfont' ".av_icon_string($key)."></span>";
		    $output .= "    <span class='entry-info-wrap'>";
		    $output .= "        <span class='entry-info'>";
		    $tc1     = "            <span class='entry-title'>{$the_title}</span>";
if($image)  $tc2     = "            <span class='entry-image'>{$image}</span>";
            $output .= $key == 'prev' ?  $tc1.$tc2 : $tc2.$tc1;
            $output .= "        </span>";
            $output .= "    </span>";
		    $output .= "</a>";
			} //end if JJA
		}
		return $output;
	}
}