    function safeTransferFrom(
        address from,
        address to,
        uint256 id,
        uint256 amount,
        bytes calldata data
    ) public {
        if (!(msg.sender == from || isApprovedForAll[from][msg.sender])) revert NotAuthorized();

        balanceOf[from][id] -= amount;

        // balance will never overflow
        unchecked {
            balanceOf[to][id] += amount;
        }

        afterTokenTransfer(from, to, id, amount);

        emit TransferSingle(msg.sender, from, to, id, amount);

-->     if (to.code.length != 0) { //@audit-issue according to EIP-1155, it MUST revert if "to" is zero address. This check is missing.
            if (
                ERC1155Holder(to).onERC1155Received(msg.sender, from, id, amount, data) !=
                ERC1155Holder.onERC1155Received.selector
            ) {
                revert UnsafeRecipient();
            }
        }
    }
// Solmate safeTransferFrom:
        require(
            to.code.length == 0
                ? to != address(0)
                : // ...
// OZ _safeTransferFrom:
        if (to == address(0)) {
            revert ERC1155InvalidReceiver(address(0));
        }
function testSuccess_afterTokenTransfer_Single_ToAddressIsZero(
        uint256 x,
        uint256 widthSeed,
        int256 strikeSeed,
        uint256 positionSizeSeed
    ) public {
        // Initial part of this test is the same as the protocol's own tests.
        _initPool(x);

        (int24 width, int24 strike) = PositionUtils.getOutOfRangeSW(
            widthSeed,
            strikeSeed,
            uint24(tickSpacing),
            currentTick
        );

        populatePositionData(width, strike, positionSizeSeed);

        /// position size is denominated in the opposite of asset, so we do it in the token that is not WETH
        uint256 tokenId = uint256(0).addUniv3pool(poolId).addLeg(
            0,
            1,
            isWETH,
            0,
            1,
            0,
            strike,
            width
        );

        sfpm.mintTokenizedPosition(
            tokenId,
            uint128(positionSize),
            TickMath.MIN_TICK,
            TickMath.MAX_TICK
        );

        // Up until this point it is the same setup as the protocol's own single transfer test.
        // We will only change the "to" address to 0.
        sfpm.safeTransferFrom(Alice, address(0), tokenId, positionSize, "");

        // The transfer is completed successfully. However, it MUST have been reverted according to the EIP standard.
        assertEq(sfpm.balanceOf(Alice, tokenId), 0);
        assertEq(sfpm.balanceOf(address(0), tokenId), positionSize);
    }    
Running 1 test for test/foundry/core/SemiFungiblePositionManager.t.sol:SemiFungiblePositionManagerTest
[PASS] testSuccess_afterTokenTransfer_Single_ToAddressIsZero(uint256,uint256,int256,uint256) (runs: 1, : 1851440, ~: 1851440)
Test result: ok. 1 passed; 0 failed; 0 skipped; finished in 8.16s
 
Ran 1 test suite: 1 test passed, 0 failed, 0 skipped (1 total test)
