Upgrading item post removal of 1st perk

If I remove the 1st perk on my legendary item using gems and then use blacksmith to successfully upgrade the item, will I get some 1st perk or the will the slot for 1st perk remain empty? Plz help.

Every time you upgrade a legendary item, the 1st perk will be filled, if it is empty. Every time you upgrade an Uber item, the 1st perkĀ and the 2nd perk will be filled, if they are empty. I do not know anything about rare items, magic items, or common items.

Thnx so much, pyromaniac