Adding unique headers to pages using custom fields

I would like to be able to add different banner images to different pages. So far I found this thread https://www.ads-software.com/support/topic/how-to-add-different-header-image-for-every-page?replies=31

I’ve created a custom field called banner and inserted the following code into my header.php

<div class="banner">
<?php if(get_post_meta($post->ID, 'banner', true)) : ?>
<img src="<?php echo get_post_meta($post->ID, 'banner', true); ?>" />
<?php else : ?>
<?php the_title(); ?>
<?php endif; ?>
<div>

However on my pages where I don’t have the banner, it’s listing the page title twice. How can I remove the page title from the code above?

Thanks