CSS custom field help

Trying to style a custom field containing an url. I use a button trick with a href class and inline span. Problem is that in case the field is empty it now shows the css elements like the background images. code:

<?php $weblink = get_post_meta($post->ID, 'weblink', true); ?>
<a href="<?php echo $weblink; ?>" class="button" target="_blank"><span>button text</span></a>

The “a href” code only needs to be printed in case the custom field is not empty, else do nothing. I’m not a coder but I’m sure this can be done in a simple way. Thanks for reply.