feat(protocol): allow ERC20Airdrop.delegateBySig to fail

packages/protocol/contracts/team/airdrop/ERC20Airdrop.sol

@@ -12,7 +12,7 @@ import "./MerkleClaimable.sol";
 contract ERC20Airdrop is MerkleClaimable {
     using SafeERC20 for IERC20;
 
-    /// @notice The address of the token contract.
+    /// @notice The address of the Taiko token contract.
     address public token;
 
     /// @notice The address of the vault contract.
@@ -72,6 +72,8 @@ contract ERC20Airdrop is MerkleClaimable {
         // client can change the data to call delegateBySig for another user.
         (address delegatee, uint256 nonce, uint256 expiry, uint8 v, bytes32 r, bytes32 s) =
             abi.decode(delegationData, (address, uint256, uint256, uint8, bytes32, bytes32));
-        IVotes(_token).delegateBySig(delegatee, nonce, expiry, v, r, s);
+
+        // Allow delegateBySig to fail to avoid potential frontfun
+        try IVotes(token).delegateBySig(delegatee, nonce, expiry, v, r, s) { } catch { }
     }
 }

packages/protocol/contracts/team/airdrop/ERC20Airdrop2.sol

@@ -22,16 +22,16 @@ contract ERC20Airdrop2 is MerkleClaimable {
     /// @notice The address of the vault contract.
     address public vault;
 
+    /// @notice Length of the withdrawal window.
+    uint64 public withdrawalWindow;
+
     /// @notice Represents the token amount for which the user has claimed.
     mapping(address addr => uint256 amountClaimed) public claimedAmount;
 
     /// @notice Represents the already withdrawn amount.
     mapping(address addr => uint256 amountWithdrawn) public withdrawnAmount;
 
-    /// @notice Length of the withdrawal window.
-    uint64 public withdrawalWindow;
-
-    uint256[45] private __gap;
+    uint256[46] private __gap;
 
     /// @notice Event emitted when a user withdraws their tokens.
     /// @param user The address of the user.

packages/protocol/test/team/airdrop/ERC20Airdrop.t.sol

@@ -209,7 +209,7 @@ contract TestERC20Airdrop is TaikoTest {
 
         delegation = abi.encode(delegatee, nonce, expiry, v, r, s);
 
-        vm.expectRevert(); // signature invalid
+        // vm.expectRevert(); // signature invalid
         vm.prank(Lily, Lily);
         airdrop.claimAndDelegate(Lily, 100, merkleProof, delegation);
     }