Fix get Balance

src/Managing.Application/Bots/Grains/AgentGrain.cs

@@ -361,7 +361,7 @@ public class AgentGrain : Grain, IAgentGrain
 
         // Get or refresh cached balance data
         var balanceData = await GetOrRefreshBalanceDataAsync(accountName);
-        if (balanceData == null)
+        if (balanceData == null || balanceData.IsValid == false)
         {
             _logger.LogError("Failed to get balance data for account {AccountName}, user {UserId}",
                 accountName, this.GetPrimaryKeyLong());
@@ -645,7 +645,7 @@ public class AgentGrain : Grain, IAgentGrain
         {
             _logger.LogError(ex, "Error fetching balance data for account {AccountName}, user {UserId}",
                 accountName, this.GetPrimaryKeyLong());
-            return null;
+            throw;
         }
     }