Only show image if custom field exists
===

How would I adjust this code to not show the image when there is no value for the custom field "imageembed"?

    <?php $imageid = get_post_meta($post->ID, 'imageembed', true); ?>
    
       <div class="newsimage"><img src="<?php echo wp_get_attachment_url( $imageid ); ?>" width="640" /></div>