Electro v2 - Change the default placeholder image for Brands in Single Product

functions.php

function electro_template_single_brand() {

    global $product;

    $product_id = electro_wc_get_product_id( $product );
    $brands_tax = electro_get_brands_taxonomy();
    $terms 		= get_the_terms( $product_id, $brands_tax );
    $brand_img 	= '';

    if ( $terms && ! is_wp_error( $terms ) ) {

        foreach ( $terms as $term ) {
            $thumbnail_id 	= defined( 'WC_VERSION' ) && version_compare( WC_VERSION, '3.6', '<' ) ? get_woocommerce_term_meta( $term->term_id, 'thumbnail_id', true ) : get_term_meta( $term->term_id, 'thumbnail_id', true );

            if ( $thumbnail_id ) {
                $image_attributes = wp_get_attachment_image_src( $thumbnail_id, 'full' );

                if( $image_attributes ) {
                    $image_src = $image_attributes[0];
                }
            } else {
                $image_src = 'https://placehold.it/150x30/';
            }

            $image_src 	= str_replace( ' ', '%20', $image_src );
            $brand_img 	.= '<a href="' . esc_url( get_term_link( $term ) ). '"><img src="' . esc_url( $image_src ) . '" alt="' . esc_attr( $term->name ) . '" /></a>';
        }
    }

    if ( ! empty( $brand_img ) ) : ?>
    <div class="brand">
        <?php echo wp_kses_post( $brand_img ); ?>
    </div>
    <?php endif;
}