It looks like the empty cards tool deletes the cards. But these are not in fact empty cards… The Anki ID I tagged is an active nephrology card in Anking v12.
In this case, the note is showing that there should be a cloze2 card so Anki is trying to show it to you even though it’s blank. By using the empty cards tool it will get rid of any ‘empty’ cards, in this case the cloze2 card that is showing up blank. It will not affect the note as a whole, or the other cards that should rightfully be present (in this case, c1 and c3+).
Please let me know if that answers your question, and if there’s anything else I can help with.
It’s most likely a typo, or an error that someone didn’t catch. It’s unusual, but not totally unheard of; almost always human error in creating the card.
I’m going to go through and edit the fix so that it doesn’t appear for anyone else going forward, but using the empty cards tool will make sure that it’s appropriate on your end ASAP.
Since we changed a c2 to c1, it will now only show c1 and c3. You don’t need a c2 for the card to work normally.
So if a card for example has
c1, c5, c7 and its missing a c2, c3, c4, and c6. That means sometime in the past its either had some clozes removed (from version of AnKing before v12) or the card was changed on AnkiHub and you can check this by clicking “View Note History”