Set timezone to null if an exception occurs.

Author: maliming

framework/src/Volo.Abp.AspNetCore.Mvc/Volo/Abp/AspNetCore/Mvc/ApplicationConfigurations/AbpApplicationConfigurationAppService.cs

@@ -332,6 +332,8 @@ protected virtual async Task<TimingDto> GetTimingConfigAsync()
             }
             catch (Exception ex)
             {
+                timeZoneId = null;
+                timeZoneName = null;
                 Logger.LogWarning(ex, $"Exception occurred while getting timezone({timeZone}) information");
             }
         }