Error when expanding ribbon (#1612)

SoftwareIdeasModeler.Core.CommandProcessing.CommandException: Exception during execution the command: ChangeTrackingSidebar ---> SoftwareIdeasModeler.Core.CommandProcessing.ActionException ---> System.NullReferenceException: Object reference not set to an instance of an object.

at SoftwareIdeasModeler.MainForm.ShowOrHideSideBarPanel(String panelID)

at SoftwareIdeasModeler.Core.CommandProcessing.ApplicationAction.<>c__DisplayClass17_0.<Perform>b__0()

--- End of inner exception stack trace ---

at SoftwareIdeasModeler.Core.CommandProcessing.ApplicationAction.Perform()

at SoftwareIdeasModeler.Core.CommandProcessing.ApplicationCommandProcessor.Execute(UnitOfWork unitOfWork, CommandDefinition commandDefinition, ActionCallback actionCallback, Object callbackTag, Boolean calledFromAnotherAction, CommandArgument[] arguments)

--- End of inner exception stack trace ---

at SoftwareIdeasModeler.Core.CommandProcessing.ApplicationCommandProcessor.Execute(UnitOfWork unitOfWork, CommandDefinition commandDefinition, ActionCallback actionCallback, Object callbackTag, Boolean calledFromAnotherAction, CommandArgument[] arguments)

at SoftwareIdeasModeler.MainForm.ribbonBar_DialogOpen(Object sender, RibbonGroupEventArgs e)

at SoftwareIdeas.Ribbon.RibbonControl.RibbonGroup.OnDialogOpening(EventArgs e)

at SoftwareIdeas.Ribbon.RibbonControl.RibbonGroup.MouseUp(MouseEventArgs e, Boolean fromFloatingGroup)

at SoftwareIdeas.Ribbon.RibbonControl.RibbonBarBody.OnMouseUp(MouseEventArgs e)

at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)

at System.Windows.Forms.Control.WndProc(Message& m)

at System.Windows.Forms.UserControl.WndProc(Message& m)

at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

OF=SoftwareIdeasModeler.MainForm

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