Handle Odd Number of Leaf Nodes in Merkle Tree Construction

[Ayush-Dutt-Sharma]

#338
Merkle tree example where an odd number of leaf nodes would result in an incorrect root hash.

Previously, the last unpaired node was skipped during hashing. This fix ensures the tree remains valid by duplicating the last node when necessary.

#Fix
Replaced the loop inside the constructor with logic that handles both even and odd numbers of nodes:

while (n > 1) {
    for (uint256 i = 0; i < n; i += 2) {
        bytes32 left = hashes[offset + i];
        bytes32 right;

        if (i + 1 < n) {
            right = hashes[offset + i + 1];
        } else {
            right = left; // duplicate last node if odd
        }

        hashes.push(keccak256(abi.encodePacked(left, right)));
    }
    offset += n;
    n = (n + 1) / 2;
}