Getting "Object reference not set to an instance of an object." error opening a Master Detail XML (4241621)

I am having an issue when opening a Master Detail XML (.xsd) file in Toad for SQL Server. I get the error below when opening one.

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Exception Information
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Exception: System.NullReferenceException
Message : Object reference not set to an instance of an object.
Stack Trace:
at Quest.Toad.MasterDetail.RelationDefinitionControl.get_IncludedObjects()
at Quest.Toad.MasterDetail.MasterDetailForm.get_Connection()
at Quest.Toad.MasterDetail.MasterDetailForm.RelationDefinitionControlOnOnEndLoad(Object sender, EventArgs eventArgs)
at Quest.Toad.ModelerDrawing.DrawingControls.DiagramControl.EndLoad()
at Quest.Toad.ModelerDrawing.DrawingControls.DiagramControl.ReadXml(XmlElement node)
at Quest.Toad.MasterDetail.RelationDefinitionControl.SetToadSet(FastSet dataset, IDocumentParameters form)
at Quest.Toad.MasterDetail.MasterDetailForm.LoadData(FastSet dataset)
at Quest.Toad.MasterDetail.MasterDetailForm.DoFileOpen(String file)
at Quest.Toad.Gui.MainForm.OpenFile(String file, PredefinedParameterCollection predefinedParameters)
at Quest.Toad.Gui.MainForm.recentFile_ItemClick(Object sender, ItemClickEventArgs e)
at DevExpress.XtraBars.BarItem.OnClick(BarItemLink link)
at DevExpress.XtraBars.BarBaseButtonItem.OnClick(BarItemLink link)
at DevExpress.XtraBars.BarItemLink.OnLinkClick()
at DevExpress.XtraBars.BarItemLink.OnLinkAction(BarLinkAction action, Object actionArgs)
at DevExpress.XtraBars.BarButtonItemLink.OnLinkAction(BarLinkAction action, Object actionArgs)
at DevExpress.XtraBars.BarItemLink.OnLinkActionCore(BarLinkAction action, Object actionArgs)
at DevExpress.XtraBars.ViewInfo.BarSelectionInfo.ClickLink(BarItemLink link)
at DevExpress.XtraBars.ViewInfo.BarSelectio