Try this:
<article>
<div class="entry-content">
<?php
$current_user = wp_get_current_user();
if ( isset( $current_user->user_email ) ) {
echo '<p>' . sprintf( __( '%s, here is your client area', 'my-theme' ), $current_user->display_name ) . ':</p>';
$output = do_shortcode( '[picu_list_collections email="' . $current_user->user_email . '"]' );
// the shortcode returns an empty <ul> tag, if there is no gallery
// https://plugins.trac.wordpress.org/browser/picu/trunk/frontend/includes/picu-template-functions.php#L464
if($output == '<ul class="picu-collection-list"></ul>') {
echo '<div class="woocommerce-MyAccount-content">
<div class="woocommerce-notices-wrapper"></div>
<div class="woocommerce-Message woocommerce-Message--info woocommerce-info">
There is no gallery.
</div>
</div>';
}
else {
echo '<div class="woocommerce-MyAccount-content">
<div class="woocommerce-notices-wrapper"></div>
<div class="woocommerce-Message woocommerce-Message--info woocommerce-info">
Your gallery.
</div>
</div>';
echo $output;
}
}
?>
</div>
</article>