Disable Level Deselection when using PMPro MMPU

pmpro-mmpu-disable-level-deselection.php

<?php

/**
 * MMPU - Prevent user from de-selecting a level if they have previously checked out for level.
 */

function pmpro_output_level_jquery_mmpu_disable() {
	if ( wp_script_is( 'jquery', 'done' ) && is_page( 'membership-levels' ) ) {
		?>
		<script>
			jQuery( '.pmpro_level-select-current input' ).prop( 'disabled', 'disabled' );
		</script>
		<?php
	}
}
add_action( 'wp_footer', 'pmpro_output_level_jquery_mmpu_disable' );