Crash when trying to open document (#1689)

A document I been creating over the last few days, Some mornings I open Document and get the Following error There are unsaved changes from the last session. Do you want to restore these changes (with a YES andNO buttons). Regardless, if I answer YES or NO to Question, software then crashes. I have done a save of the document whenever I close it, so it doesn't have unsaved changes. I end up going back to a previous day backup losing changes I made. Here is the Crash......

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

at SoftwareIdeas.Common.TextRendering.ParagraphStyle.FromXElement(XElement xElem)

at SoftwareIdeas.Common.TextRendering.NumberingLevel.FromXElement(XElement xElem)

at SoftwareIdeas.Common.TextRendering.Numbering.FromXElement(XElement xElem)

at SoftwareIdeas.Common.TextRendering.ParagraphStyle.FromXElement(XElement xElem)

at SoftwareIdeas.Common.TextRendering.ParagraphDefinition.FromXElement(XElement xelem)

at SoftwareIdeas.Common.TextRendering.FormattedParagraph.FromXElement(FormattedText owner, XElement paragraphElem)

at SoftwareIdeas.Common.TextRendering.FormattedText.LoadFromXml(XElement xElement, Boolean convertNullToEmpty)

at SoftwareIdeasModeler.Core.Projecting.ModelElementBase.SetFromXElement(SimXmlReader reader, Project project, XElement xelem)

at SoftwareIdeasModeler.ProjectXml.SimXmlReader.LoadModelElement(SimXmlReader reader, Project project, XElement xelement)

at SoftwareIdeasModeler.ProjectXml.SimXmlReader.LoadElements(XElement root)

at SoftwareIdeasModeler.ProjectXml.SimXmlReader.Load()

at SoftwareIdeasModeler.ProjectHelper.LoadProject(String localFileName, Boolean showReadOnlyWarning, Boolean checkFileVersion, Boolean processCustomDiagrams, Boolean showErrorMessages)

at SoftwareIdeasModeler.ProjectHelper.LoadProject(String filename, String repositoryPath, Boolean showReadOnlyWarning)