Override image size that may not exist within genesis_get_image

functions.php

<?php
/**
 * functions.php
 * 
 * In reply to Genesis Support forums.
 * http://www.studiopress.com/forums/topic/maximum-width-and-height-of-images-in-winning-agent-pro-theme/
 */

add_filter( 'genesis_pre_get_image', 'custom_genesis_pre_get_image', 10, 3 );
/**
 * Callback for Genesis 'genesis_pre_get_image' filter.
 *
 * Override the image size if specified as 'properties'.
 *
 * @param  bool     $check  The return value.  Default false.
 * @param  array    $args   The arguments for genesis_get_image()
 * @param  object   $post   The current post object.
 * @return mixed            The output.  If the return value is false, this will be ignored.
 */
function custom_genesis_pre_get_image( $check, $args, $post ){
    
    if( isset( $args['size'] ) && 'properties' !== $args['size'] )
        return $check;

    return genesis_get_image( array( 'size' => 'medium' ) );

}