Notice: Undefined index: pretext…

Quick solution:

//We'll want to switch between the two breadcrumb output types
		if($instance['type'] == 'list')
		{
			//Display the list output breadcrumb
			if (isset($instance['pretext'])) {
				echo $instance['pretext'];
			}
			echo '<ol class="breadcrumb_trail breadcrumbs">';
			bcn_display_list(false, $instance['linked'], $instance['reverse']);
			echo '</ol>';
		}