[ERC721] Delete approved if have

[rotcivegaf]

Description

Clear getApproved only if have an approved address

Statistically, this would save gas, the sum of an owner transfer and isApprovedForAll transfer is greater than an approved transfer

Save 80 gas if the getApproved haven't a approved
Spend 150 gas if the getApproved have a approved
(In each transferFrom, according to my tests)

Checklist

Ensure you completed all of the steps below before submitting your pull request:

• Ran forge snapshot?
• Ran npm run lint?
• Ran forge test?

Pull requests with an incomplete checklist will be thrown out.

[rotcivegaf]

What do you think about:

• Emitting the Approval event if the approved is cleared?
• Use the same pattern in the _burn function

[transmissions11]

uh ser i dont see any changes in the diff... and you've installed solmate... in solmate?

[transmissions11]

i'd like to see the diffs before i comment on those changes (im a codecel lol i cant think in human terms)

[Vectorized]

Wow, this actually does work. But the code is missing.

@rotcivegaf Thanks for the suggestion! Will credit you on the next release of ERC721A.

We don't need to emit an Approval event in this case, as the Transfer event will be sufficient to signal the reset of any approval. chiru-labs/ERC721A#274

[rotcivegaf]

Sorry, I needed to sleep, I forgot push the change...
Check #255 PR