show the "notify me" button while "non inventory" variants are unselected

In the situation where an inventory item on a product is out of stock but there are certain optional addons that are part of a non-inventory variant group, none of which are selected by default, the "notify me" button does not currently show up until one of those non-inventory optional addons are selected.

In my opinion, the notify me button logic should only be with relation to the inventory items, and should ignore whether or not the non-inventory variants have been selected. 

The workaround for this is of course to make a default "no addon" option in that variant group, but this adds unnecessary clutter to the receipts, invoices, and packing slips that really doesn't need to be there.

Thanks!