fix: unstake before staking starts

src/libs/LibTokenizedVaultStaking.sol

@@ -190,7 +190,7 @@ library LibTokenizedVaultStaking {
         // staker's balance in the past are never adjusted
         // stakers and NLF balances are adjusted in the current interval when unstaking
         // in the current interval, if a reward was paid and therefor collected, staking distribution need to be adjusted according to the balances
-        if (lastPaidInterval == currentInterval) {
+        if (lastPaidInterval == currentInterval && currentInterval != 0) {
             bytes32 vTokenIdLastPaid = _vTokenId(_entityId, tokenId, lastPaidInterval);
             s.stakingDistributionAmount[vTokenIdLastPaid] -= (s.stakingDistributionAmount[vTokenIdLastPaid] * userStateAtLastPaid.balance) / totalStateAtLastPaid.balance;
         }

test/T06Staking.t.sol

@@ -678,6 +678,28 @@ contract T06Staking is D03ProtocolDefaults {
         assertEq(getRewards(lou.entityId, nlf.entityId), 0, "Lou's reward [5] should be zero".red());
     }
 
+    function test_stakeUnstakeBeforeInit() public {
+        initStaking(4 * I);
+
+        vm.warp(2 * I + 10 days); // important not to stake at [0] interval!
+
+        uint256 balanceBefore = nayms.internalBalanceOf(bob.entityId, usdcId);
+
+        startPrank(bob);
+        nayms.stake(nlf.entityId, bobStakeAmount);
+        startPrank(sue);
+        nayms.stake(nlf.entityId, sueStakeAmount);
+        startPrank(lou);
+        nayms.stake(nlf.entityId, louStakeAmount);
+
+        startPrank(bob);
+        nayms.unstake(nlf.entityId);
+
+        assertEq(nayms.internalBalanceOf(bob.entityId, usdcId), balanceBefore, "balance should be the same");
+        assertStakedAmount(sue.entityId, sueStakeAmount, "Sue's staked amount should be the same".red());
+        assertStakedAmount(lou.entityId, louStakeAmount, "Lou's staked amount should be the same".red());
+    }
+
     function test_skipPayingAnInterval() public {
         uint256 startStaking = block.timestamp + 100 days;
         initStaking(startStaking);