Attaching files to component - Error: Object reference not set to an instance of an object.

If you receive the following error message when attaching files:

System.NullReferenceException: Object reference not set to an instance of an object.

at TmMv2.FrmTmMv2ComponentDocumentDialog.Init(TmFile FileEnt, TmComponent ComponentEnt, TmComponentToReqDoc Link)

at TmMv2.CtlTmMv2File.AddFile(String file, String description)

You need to save the component before attaching the file.