add artifacts to .gitignore

artifacts/contracts/p2pix.sol/P2PIX.dbg.json

@@ -0,0 +1,4 @@
+{
+  "_format": "hh-sol-dbg-1",
+  "buildInfo": "../../build-info/eceac9979aa58fac0d83cf0060ae7a91.json"
+}

contracts/p2pix.sol

@@ -150,10 +150,12 @@ contract P2PIX is BaseUtils {
         uint256 bal = getBalance(args.seller, args.token);
         if (bal < args.amount) revert NotEnoughTokens();
 
-        uint256 c = lockCounter + 1;
+        unchecked { 
+            lockID = ++lockCounter;
+        }
 
         if (
-            mapLocks[c].expirationBlock >= block.number
+            mapLocks[lockID].expirationBlock >= block.number
         ) revert NotExpired();
 
         address sender; uint256 forwarder;
@@ -178,7 +180,7 @@ contract P2PIX is BaseUtils {
         }
 
         DT.Lock memory l = DT.Lock(
-            c,
+            lockID,
             (block.number + defaultLockBlocks),
             _pixTarget,
             args.amount,
@@ -383,12 +385,10 @@ contract P2PIX is BaseUtils {
     function _addLock(
         uint256 _bal,
         DT.Lock memory _l
-    ) internal returns(uint256 counter){
+    ) internal {
         mapLocks[_l.counter] = _l;
 
         _decBal(_bal, _l.amount, ERC20(_l.token), _l.seller);
-        ++lockCounter;
-        counter = _l.counter;
 
         emit LockAdded(
             _l.buyerAddress,