Remove states instead setting Null.Value

* Renamed all occurrances of "SetLegaceState(_, Null.Value)" to "RemoveLegaceState(_)"

* Updated Test files to Assert Null instead of Null.Value

---------

Co-authored-by: Lee Dogeon <dev.moreal@gmail.com>

.Lib9c.DevExtensions.Tests/Action/CreateOrReplaceAvatarTest.cs

@@ -562,7 +562,7 @@ private static void Execute(
                 Addresses.GetSkillStateAddressFromAvatarAddress(avatarAddr.Value);
             if (action.CrystalRandomBuff is null)
             {
-                Assert.Equal(Null.Value, nextStates.GetLegacyState(crystalRandomSkillAddr));
+                Assert.Null(nextStates.GetLegacyState(crystalRandomSkillAddr));
             }
             else
             {

.Lib9c.Tests/Action/ClaimStakeRewardTest.cs

@@ -362,7 +362,7 @@ public void Execute_Throw_FailedLoadStateException_When_Staking_State_Null()
                     0));
 
             var stakeAddr = StakeStateV2.DeriveAddress(AgentAddr);
-            var previousState = _initialState.SetLegacyState(stakeAddr, Null.Value);
+            var previousState = _initialState.RemoveLegacyState(stakeAddr);
             Assert.Throws<FailedLoadStateException>(() =>
                 Execute(
                     previousState,
@@ -447,7 +447,7 @@ public void Execute_Throw_FailedLoadStateException_When_Sheet_Null()
             // NOTE: Set StakeRegularFixedRewardSheetTable to Null
             var sheetAddr = Addresses.GetSheetAddress(
                 stakeStateV2.Contract.StakeRegularFixedRewardSheetTableName);
-            prevState = prevState.SetLegacyState(sheetAddr, Null.Value);
+            prevState = prevState.RemoveLegacyState(sheetAddr);
             Assert.Throws<FailedLoadStateException>(() =>
                 Execute(
                     prevState,
@@ -462,7 +462,7 @@ public void Execute_Throw_FailedLoadStateException_When_Sheet_Null()
             // NOTE: Set StakeRegularRewardSheetTableName to Null
             sheetAddr = Addresses.GetSheetAddress(
                 stakeStateV2.Contract.StakeRegularRewardSheetTableName);
-            prevState = prevState.SetLegacyState(sheetAddr, Null.Value);
+            prevState = prevState.RemoveLegacyState(sheetAddr);
             Assert.Throws<FailedLoadStateException>(() =>
                 Execute(
                     prevState,

.Lib9c.Tests/Action/EndPledgeTest.cs

@@ -37,7 +37,7 @@ public void Execute(int balance)
                 Signer = patron,
                 PreviousState = states,
             });
-            Assert.Equal(Null.Value, nextState.GetLegacyState(agent.GetPledgeAddress()));
+            Assert.Null(nextState.GetLegacyState(agent.GetPledgeAddress()));
             Assert.Equal(mead * 0, nextState.GetBalance(agent, mead));
             if (balance > 0)
             {

.Lib9c.Tests/Action/Garages/DeliverToOthersGaragesTest.cs

@@ -243,7 +243,7 @@ public void Execute_Throws_Exception()
                     SenderAgentAddr,
                     fungibleId);
                 var previousStatesWithNullGarageState =
-                    _previousStates.SetLegacyState(garageAddr, Null.Value);
+                    _previousStates.RemoveLegacyState(garageAddr);
                 Assert.Throws<StateNullException>(() => Execute(
                     SenderAgentAddr,
                     0,

.Lib9c.Tests/Action/Garages/UnloadFromMyGaragesTest.cs

@@ -255,7 +255,7 @@ public void Execute_Throws_Exception()
                     AgentAddr,
                     fungibleId);
                 var previousStatesWithNullGarageState =
-                    _previousStates.SetLegacyState(garageAddr, Null.Value);
+                    _previousStates.RemoveLegacyState(garageAddr);
                 Assert.Throws<StateNullException>(() => Execute(
                     AgentAddr,
                     0,

.Lib9c.Tests/Action/Scenario/MarketScenarioTest.cs

@@ -321,7 +321,7 @@ public void Register_And_Buy()
                     var sellProductList = new ProductsState((List)latestState.GetLegacyState(ProductsState.DeriveAddress(productInfo.AvatarAddress)));
                     var productId = productInfo.ProductId;
                     Assert.Empty(sellProductList.ProductIds);
-                    Assert.Equal(Null.Value, latestState.GetLegacyState(Product.DeriveAddress(productId)));
+                    Assert.Null(latestState.GetLegacyState(Product.DeriveAddress(productId)));
                     var product = ProductFactory.DeserializeProduct((List)nextState2.GetLegacyState(Product.DeriveAddress(productId)));
                     switch (product)
                     {
@@ -508,7 +508,7 @@ public void Register_And_Cancel()
 
             foreach (var productAddress in action2.ProductInfos.Select(productInfo => Product.DeriveAddress(productInfo.ProductId)))
             {
-                Assert.Equal(Null.Value, latestState.GetLegacyState(productAddress));
+                Assert.Null(latestState.GetLegacyState(productAddress));
                 var product = ProductFactory.DeserializeProduct((List)nextState.GetLegacyState(productAddress));
                 switch (product)
                 {
@@ -1097,7 +1097,7 @@ public void HardFork()
                     var sellProductList = new ProductsState((List)tradedState.GetLegacyState(ProductsState.DeriveAddress(productInfo.AvatarAddress)));
                     var productId = productInfo.ProductId;
                     Assert.Empty(sellProductList.ProductIds);
-                    Assert.Equal(Null.Value, tradedState.GetLegacyState(Product.DeriveAddress(productId)));
+                    Assert.Null(tradedState.GetLegacyState(Product.DeriveAddress(productId)));
                     var product = ProductFactory.DeserializeProduct((List)nextState.GetLegacyState(Product.DeriveAddress(productId)));
                     switch (product)
                     {

.Lib9c.Tests/Action/Stake2Test.cs

@@ -208,7 +208,7 @@ public void Execute()
                 BlockIndex = StakeState.LockupInterval,
             });
 
-            Assert.Equal(Null.Value, states.GetLegacyState(stakeState.address));
+            Assert.Null(states.GetLegacyState(stakeState.address));
             Assert.Equal(_currency * 0, states.GetBalance(stakeState.address, _currency));
             Assert.Equal(_currency * 100, states.GetBalance(_signerAddress, _currency));
         }

Lib9c.DevExtensions/Action/CreateOrReplaceAvatar.cs

@@ -582,7 +582,7 @@ public IWorld Execute(
                 Addresses.GetSkillStateAddressFromAvatarAddress(avatarAddr);
             if (CrystalRandomBuff is null)
             {
-                states = states.SetLegacyState(crystalRandomSkillAddr, Null.Value);
+                states = states.RemoveLegacyState(crystalRandomSkillAddr);
             }
             else
             {

Lib9c/Action/BuyProduct.cs

@@ -178,7 +178,7 @@ private IWorld Buy(IActionContext context, IProductInfo productInfo, Address sel
             var receipt = new ProductReceipt(productId, sellerAvatarAddress, buyerAvatarState.address, product.Price,
                 context.BlockIndex);
             states = states
-                .SetLegacyState(productAddress, Null.Value)
+                .RemoveLegacyState(productAddress)
                 .SetLegacyState(productsStateAddress, productsState.Serialize())
                 .SetAvatarState(sellerAvatarAddress, sellerAvatarState)
                 .SetLegacyState(ProductReceipt.DeriveAddress(productId), receipt.Serialize())

Lib9c/Action/CancelProductRegistration.cs

@@ -181,7 +181,7 @@ public static IWorld Cancel(
 
             var mail = new ProductCancelMail(context.BlockIndex, productId, context.BlockIndex, productId, product);
             avatarState.Update(mail);
-            states = states.SetLegacyState(productAddress, Null.Value);
+            states = states.RemoveLegacyState(productAddress);
             return states;
         }
 

Lib9c/Action/EndPledge.cs

@@ -44,7 +44,7 @@ public override IWorld Execute(IActionContext context)
                 {
                     states = states.TransferAsset(context, AgentAddress, signer, balance);
                 }
-                return states.SetLegacyState(contractAddress, Null.Value);
+                return states.RemoveLegacyState(contractAddress);
             }
 
             throw new FailedLoadStateException("failed to find pledge.");

Lib9c/Action/MigrateMonsterCollection.cs

@@ -90,7 +90,7 @@ public override IWorld Execute(IActionContext context)
 
             var ended = DateTimeOffset.UtcNow;
             Log.Debug("{AddressesHex}MigrateMonsterCollection Total Executed Time: {Elapsed}", addressesHex, ended - started);
-            return states.SetLegacyState(monsterCollectionState.address, Null.Value)
+            return states.RemoveLegacyState(monsterCollectionState.address)
                 .SetLegacyState(migratedStakeStateAddress, migratedStakeState.SerializeV2())
                 .TransferAsset(
                     context,

Lib9c/Action/Stake2.cs

@@ -122,7 +122,7 @@ public override IWorld Execute(IActionContext context)
                 if (stakeState.IsCancellable(context.BlockIndex))
                 {
                     return states
-                        .SetLegacyState(stakeState.address, Null.Value)
+                        .RemoveLegacyState(stakeState.address)
                         .TransferAsset(context, stakeState.address, context.Signer, stakedBalance);
                 }
             }