Locked Collections Allow Mint of New NFT if NFT is Burned

[HashWarlock]

When calling lock_collection the function will get the CollectionInfo for the specified collection_id and will set the max field to the field nfts_count. Since the max is now set to nfts_count the issuer can no longer mint anymore NFTs within the collection. However, if an NFT owner were to call burn_nft then the Collection issuer can now call mint_nft and be able to mint an NFT is a locked Collection.

Possible solutions:

• When locking a collection, the issuer of the collection is set to a burner address that is inaccessible. This prevents anyone from minting new NFTs.
• Instead of setting the max field to nfts_count, set max to 0. This prevents a new mint no matter the case as the check here should prevent a new mint:

rmrk-substrate/pallets/rmrk-core/src/functions.rs

Lines 349 to 352 in 405af24

	// Prevent minting when nfts_count is greater than the collection max.
	if let Some(max) = collection.max {
	ensure!(collection.nfts_count < max, Error::<T>::CollectionFullOrLocked);
	}

rmrk-substrate/pallets/rmrk-core/src/functions.rs

Lines 433 to 435 in 405af24

	if let Some(max) = collection.max {
	ensure!(collection.nfts_count < max, Error::<T>::CollectionFullOrLocked);
	}

[bmacer]

#215 implements the second proposed solution, which is much simpler than the first. unless there's some other use/value for the max variable, i thinking setting it to 0 is the ideal solution for this issue.

[bmacer]

Pretty sure this can be closed