diff --git a/IoTGateway.ViewModel/BasicData/DeviceVariableVMs/DeviceVariableListVM.cs b/IoTGateway.ViewModel/BasicData/DeviceVariableVMs/DeviceVariableListVM.cs
index 6515368..c94f34d 100644
--- a/IoTGateway.ViewModel/BasicData/DeviceVariableVMs/DeviceVariableListVM.cs
+++ b/IoTGateway.ViewModel/BasicData/DeviceVariableVMs/DeviceVariableListVM.cs
@@ -45,10 +45,12 @@ namespace IoTGateway.ViewModel.BasicData.DeviceVariableVMs
                 foreach (var item in device.Children)
                 {
                     var deviceThread = deviceService.DeviceThreads.Where(x => x._device.ID.ToString() == (string)item.Value).FirstOrDefault();
+                    if (deviceThread != null)
+                        item.Icon = deviceThread._device.AutoStart ? (deviceThread._driver.IsConnected ? "layui-icon-link" : "layui-icon-unlink") : "layui-icon-pause";
 
                     item.Text = item.Text;
-                    item.Icon = deviceThread._device.AutoStart ? (deviceThread._driver.IsConnected ? "layui-icon-link" : "layui-icon-unlink") : "layui-icon-pause";
                     item.Expended = true;
+
                 }
             }
             DevicesTree = GetLayuiTree(AllDevices);
diff --git a/IoTGateway/iotgateway.db b/IoTGateway/iotgateway.db
index f132ff4..a3604a0 100644
Binary files a/IoTGateway/iotgateway.db and b/IoTGateway/iotgateway.db differ
diff --git a/iotgateway.db b/iotgateway.db
index 1fe8438..a3604a0 100644
Binary files a/iotgateway.db and b/iotgateway.db differ