fix: 移除商户中心租户信息兜底返回

src/Application/TakeoutSaaS.Application/App/Merchants/Handlers/GetCurrentMerchantCenterQueryHandler.cs

@@ -62,7 +62,8 @@ public sealed class GetCurrentMerchantCenterQueryHandler(
         // 5. 读取商户主体与租户信息
         var merchant = await merchantRepository.FindByIdAsync(merchantId, currentTenantId, cancellationToken)
             ?? throw new BusinessException(ErrorCodes.NotFound, "商户不存在");
-        var tenant = await tenantRepository.FindByIdAsync(currentTenantId, cancellationToken);
+        var tenant = await tenantRepository.FindByIdAsync(currentTenantId, cancellationToken)
+            ?? throw new BusinessException(ErrorCodes.NotFound, "租户不存在");
 
         // 6. 读取商户关联数据
         var stores = await storeRepository.GetByMerchantIdAsync(merchantId, currentTenantId, cancellationToken);
@@ -77,7 +78,7 @@ public sealed class GetCurrentMerchantCenterQueryHandler(
         var staffDtos = staffs.Select(StoreMapping.ToDto).ToList();
         return new CurrentMerchantCenterDto
         {
-            Merchant = MerchantMapping.ToDetailDto(merchant, tenant?.Name, storeDtos),
+            Merchant = MerchantMapping.ToDetailDto(merchant, tenant.Name, storeDtos),
             Staffs = staffDtos,
             Documents = MerchantMapping.ToDocumentDtos(documents),
             Contracts = MerchantMapping.ToContractDtos(contracts),