Better solution for the image output

Use this in line smart-posts.php:122

<br />
          <div class="left"><br />
  					<a>" title="<?php the_title_attribute(); ?>"><br />
  					 <?php the_post_thumbnail(array($instance["thumb_w"], $instance["thumb_h"])); ?><br />
  					</a><br />
          </div><br />
				<?php endif; ?><br />

Instead of using the style attribute, resize the thumbnail via:

the_post_thumbnail(array($instance["thumb_w"], $instance["thumb_h"]));

https://wordpress.org/plugins/smart-posts-widget/