if statement for featured images

Question

I'm just looking to make sure my home page and pages display my featured image if set, and other wise if not set show blog-banner.jpg. So that's what I thought I had however now my 404 error page doesn't have a banner image. Any advice on correcting this if statement?

/** Add the featured image section */
add_action( 'genesis_before_header', 'minimum_featured_image' );
function minimum_featured_image() {

global $post; 
$post->ID;

if ( is_home() ) {
    echo '<div id="featured-image-home">';
    echo get_the_post_thumbnail($thumbnail->ID, 'header');
    echo '</div>';
}
if ( is_singular( array( 'post' ) ) && ( !has_post_thumbnail( $post->ID ) ) ){
    echo '<div id="featured-image-home"><img src="'. get_stylesheet_directory_uri() . '/images/blog-banner.jpg" /></div>';
    return;
}
if ( is_singular( array( 'post', 'page' ) ) && has_post_thumbnail( $post->ID ) ){
    echo '<div id="featured-image">';
    echo get_the_post_thumbnail($thumbnail->ID, 'header');
    echo '</div>';
}
}

Answer 1

The second if statement requires it to be a post, so a 404 page won't pass.

I'd re-do it like this, using elseif statements. I also changed $thumbnail->ID to $post->ID since the former was not defined.

add_action( 'genesis_before_header', 'minimum_featured_image' );
function minimum_featured_image() {

    global $post; 

    if ( is_home() ) {
        echo '<div id="featured-image-home">';
        echo get_the_post_thumbnail($post->ID, 'header');
        echo '</div>';
    }
    elseif ( is_singular( array( 'post' , 'page' ) ) && ( !has_post_thumbnail( $post->ID ) ) ){
        echo '<div id="featured-image">';
        echo get_the_post_thumbnail($post->ID, 'header');
        echo '</div>';
    }   
    elseif(is_singular( array( 'post' , 'page' ) ){
        echo '<div id="featured-image-home"><img src="'. get_stylesheet_directory_uri() . '/images/blog-banner.jpg" /></div>';
    }
} 

Answer 2

You need one more conditional

if ( is_404() ) {
    // your code here
}

Your function:

add_action( 'genesis_before_header', 'minimum_featured_image' );
function minimum_featured_image() {

global $post; 

if ( is_home() ) {
    echo '<div id="featured-image-home">';
    echo get_the_post_thumbnail($post->ID, 'header');
    echo '</div>';
}
elseif ( is_singular( array( 'post' , 'page' ) ) && ( !has_post_thumbnail( $post->ID ) ) ){
    echo '<div id="featured-image">';
    echo get_the_post_thumbnail($post->ID, 'header');
    echo '</div>';
}   
elseif( is_singular( array( 'post' , 'page' ) ) ) {
    echo '<div id="featured-image-home"><img src="'. get_stylesheet_directory_uri() . '/images/blog-banner.jpg" /></div>';
}
elseif( is_404() ) {
    echo '<div id="featured-image-home"><img src="'. get_stylesheet_directory_uri() . '/images/blog-banner.jpg" /></div>';
}

}

You might also want to check the rest of the conditional tags