Thats a very powerfull thing indeed!
(Also:)
Soo, dev note on this. The empty parts were just meant to be "make new sword" part and also save data corruption default to prevent the game from crashing. We gave it a rarity of "Infinity" so it would not show up in either the shop or battle, but. When you try "getRandomPartBasedRarity" it caused an infinite loop XD
In a panic we just put the rarity to 1 fixing the game, but causing this hilarious side effect XD