fix(x/ecocredit): remove fee param when amount is zero

x/ecocredit/base/keeper/features/msg_update_class_fee.feature

@@ -68,3 +68,21 @@ Feature: Msg/MsgUpdateClassFee
         "fee": {}
       }
       """
+
+    Scenario: the class fee is removed when amount is zero
+      When alice attempts to update class fee with properties
+      """
+      {
+        "authority":"regen1nzh226hxrsvf4k69sa8v0nfuzx5vgwkczk8j68",
+        "fee":{
+          "denom": "uregen",
+          "amount": "0"
+        }
+      }
+      """
+      Then expect class fee with properties
+      """
+      {
+        "fee": {}
+      }
+      """

x/ecocredit/base/keeper/msg_update_class_fee.go

@@ -17,7 +17,7 @@ func (k Keeper) UpdateClassFee(ctx context.Context, req *types.MsgUpdateClassFee
 	}
 
 	var classFee *sdkv1beta1.Coin
-	if req.Fee != nil {
+	if req.Fee != nil && req.Fee.IsPositive() {
 		classFee = regentypes.CoinToProtoCoin(*req.Fee)
 	}
 

x/ecocredit/basket/keeper/features/msg_update_basket_fee.feature

@@ -70,3 +70,22 @@ Feature: Msg/MsgUpdateBasketFee
         "fee": {}
       }
       """
+
+    Scenario: the basket fee is removed when amount is zero
+      When alice attempts to update basket fee with properties
+      """
+      {
+        "authority":"regen1nzh226hxrsvf4k69sa8v0nfuzx5vgwkczk8j68",
+        "fee": {
+          "denom": "uregen",
+          "amount": "0"
+        }
+      }
+      """
+      Then expect no error
+      And expect basket fee with properties
+      """
+      {
+        "fee": {}
+      }
+      """

x/ecocredit/basket/keeper/msg_update_basket_fee.go

@@ -19,7 +19,7 @@ func (k Keeper) UpdateBasketFee(ctx context.Context, req *types.MsgUpdateBasketF
 
 	var basketFee *sdkv1beta1.Coin
 
-	if req.Fee != nil {
+	if req.Fee != nil && req.Fee.IsPositive() {
 		basketFee = regentypes.CoinToProtoCoin(*req.Fee)
 	}