I have error message.

I have error message as follows:

System.Xml.XmlNode ImportNodeInternal(System.Xml.XmlNode, Boolean): Cannot import a null node.
0: at System.Xml.XmlDocument.ImportNodeInternal(XmlNode node, Boolean deep)
1: at ECT.ECAD.API.SystemSetup.RestoreNodeFromVariableParts(WorksetConfig worksetConfig, XmlNode configNode)
2: at ECT.ECAD.API.SystemSetup.RestoreNodeFromVariable(XmlDocument doc)
3: at ECT.ECAD.API.SystemSetup.Restore()
4: at ECT.ECAD.API.SystemSetup..ctor()
5: at ECT.ECAD.API.SystemSetup.Recreate()
6: at Bentley.Electrical.UI.Command.CommandEntryServiceBase.Init(Int32 hwndMode, Int32 hwndLayer)