// Find this code in both the index.php and single.php files:

<img src="<?php echo get_post_meta($post->ID, "post_image_value", $single = true); ?>" alt="<?php the_title(); ?>" width="250" />

// Change it to this:

<?php if(get_post_meta($post->ID, "post_image_value", $single = true) != "") { ?>
 <img src="<?php echo get_post_meta($post->ID, "post_image_value", $single = true); ?>" alt="<?php the_title(); ?>" width="250" />
<?php } ?>