Product Custom Validation not working with snippet

Hi,
On Admin Dashboard in Product Custom validation I made required:
Price
Featured Image
Categories

But when vendor adds a product without filling in any fields only error messages are showing for:
Price
Product Title
Featured Image

The category part has a required asterix but vendor can still add product without choosing a category.
I think this is because of a snippet I used from this forum to restrict vendor to add a product in the main category (which works very well by the way).
When I remove the snippet from my child theme’s functions.php the message of required category is visible when vendor tries to publish his product.

The snippet I used:

// Main category restriction

function wcfm_pm_custom_script( $end_point ) {
	switch( $end_point ) {
		case 'wcfm-products-manage':
			?>
			<script>
			jQuery(document).ready(function($) {
				$('#product_cats_checklist').children('.product_cats_checklist_item').each(function() {
					if( $(this).children('.product_taxonomy_sub_checklist').length > 0 ) {
					  $(this).children('label').children('input').addClass('wcfm_custom_hide');
					}
				});
			});
			</script>
		<?php
		break;
  }
}
add_action( 'after_wcfm_load_views', 'wcfm_pm_custom_script' );

Is there any way I can keep this snippet but with the required category choosing message when vendor forgets to pick a category?

Thank you!