Cyjan zec mutex 2 (#3569)

* fix: mutex on zec

* refactor: simplify orchard migratable balance checks and update related methods

lib/view_model/dashboard/dashboard_view_model.dart

@@ -96,7 +96,6 @@ abstract class DashboardViewModelBase with Store {
         isShowFirstYatIntroduction = false,
         isShowSecondYatIntroduction = false,
         isShowThirdYatIntroduction = false,
-        isMigratingToIronwood = false,
         filterItems = [],
         exchangeFilterItems = [],
         subname = '',
@@ -251,8 +250,6 @@ abstract class DashboardViewModelBase with Store {
 
     reaction((_) => tradesStore.trades, (_) => tradeMonitor.monitorActiveTrades(wallet.id));
 
-    addZcashMigrationReaction();
-
     tradeMonitor.monitorActiveTrades(wallet.id);
   }
 
@@ -377,21 +374,9 @@ abstract class DashboardViewModelBase with Store {
     );
   }
 
-  @observable
-  ReactionDisposer? zcashMigrationReactionDisposer;
-
-  @action
-  void addZcashMigrationReaction()  {
-    zcashMigrationReactionDisposer?.reaction.dispose();
-    zcashMigrationReactionDisposer = null;
-
-    if (wallet.type == WalletType.zcash) {
-      zcashMigrationReactionDisposer = reaction((_) => wallet.balance.values.first, (_) async {
-        isMigratingToIronwood =
-            wallet.type == WalletType.zcash && await zcash!.hasOrchardMigratableBalance(wallet);
-      });
-    }
-  }
+  @computed
+  bool get isMigratingToIronwood =>
+      wallet.type == WalletType.zcash && (zcash?.hasOrchardMigratableBalance(wallet) ?? false);
 
   @computed
   bool get isSyncHeavy {
@@ -1289,8 +1274,6 @@ abstract class DashboardViewModelBase with Store {
     name = wallet.name;
     loadFilterItems();
 
-    addZcashMigrationReaction();
-
     if (wallet.type == WalletType.monero) {
       subname = monero!.getCurrentAccount(wallet).label;
 
@@ -1572,9 +1555,6 @@ abstract class DashboardViewModelBase with Store {
     }
   }
 
-  @observable
-  bool isMigratingToIronwood;
-
   String getTransactionType(TransactionInfo tx) {
     if (wallet.type == WalletType.bitcoin) {
       if (tx.isReplaced == true) return ' (replaced)';