Require minimum file uploads when using WP Job Manager Field Editor

functions.php

<?php
add_filter( 'submit_job_form_validate_fields', 'smyles_check_min_upload_files', 9999, 3 );

/**
 * Check Min Uploaded Files
 *
 * @param $no_errors
 * @param $fields
 * @param $values
 *
 * @return \WP_Error|true
 * @since @@version
 *
 */
function smyles_check_min_upload_files( $no_errors, $fields, $values ){

	$min_uploads = 4;
	$error_message = sprintf( __( 'The minimum files is %1$s for %2$s' ), $min_uploads, __( 'Gallery Images' ) );

	if( ! isset( $values['job'], $values['job']['gallery_images'] ) ){
		return new WP_Error( 'validation-error', $error_message );
	}

	if( count( $values['job']['gallery_images'] ) < $min_uploads ){
		return new WP_Error( 'validation-error', $error_message );
	}

	return $no_errors;
}