NFT issuer is inadvertently creating a trustline due to third-party transactions(Version: 2.1.0)

[tequdev]

Issue Description

Since the NFTokenAcceptOffer does not check the trust line that the issuer receives as a transfer fee in the NFTokenAcceptOffer, if the issuer deletes the trust line after NFTokenCreateOffer, the trust line is created for the issuer by the NFTokenAcceptOffer.

Steps to Reproduce

1. Issuer has Trustline (ie: USD)
2. Mint NFToken with transfer fee
3. Transfer NFToken to Alice.
4. Alice create NFTokenOffer to bob with 10 USD
5. Issuer delete USD Trustline
6. Accept NFTokenOffer

Expected Result

NFTokenAcceptOffer transaction fails with terNO_LINE

Actual Result

NFTokenAcceptOffer transaction succeeds and a trustline is created for the issuer.

Environment

rippled 2.1.0

Supporting Files

https://gist.github.com/tequdev/f5cfd3f3cfbfcf4a22205052962e6cfe

[ximinez]

Do you have any example transaction(s)?

[tequdev]

Do you have any example transaction(s)?

You can find gist code in the supporting files.

[ximinez]

Yes, that's the code you used to generate transaction, but what I'm asking for is transaction IDs that have already been validated, and which network they're on.

[tequdev]

This NFTokenAcceptOffer transaction creates a trustline for NFT's Issuer account.

https://testnet.xrpl.org/transactions/DB9EC35BEC75D314CAB5D4ADBF676C0ACE4EF03EAA83268921C377CD0ACF4934/detailed

NFToken issuer account https://testnet.xrpl.org/accounts/rL4qyVGJLjch4863okbM9brrR5EhFrHZ61

[ximinez]

Yep. Confirmed that this is a legitimate issue.