Application crash when pasting (#261)

I get the following error when I try to paste as a new instance a block declared in another block diagram:

System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.

at System.ThrowHelper.ThrowKeyNotFoundException()

at System.Collections.Generic.Dictionary`2.get_Item(TKey key)

at SoftwareIdeasModeler.Core.DiagramItems.MultiPartElements.ConcreteMultiPartElement.DrawElement(DiagramDrawer drawer, DrawingParameters param)

at SoftwareIdeasModeler.Core.Projecting.ConcreteDiagramItem.Draw(DiagramDrawer drawer, DrawingParameters param)

at SoftwareIdeasModeler.Visualisation.DiagramDrawer.Draw(DiagramLayer layer, ConcreteDiagramItem item)

at SoftwareIdeasModeler.Visualisation.DiagramDrawer.Draw(DiagramLayer layer, Rectangle clipArea)

at SoftwareIdeasModeler.Visualisation.DiagramDrawer.Draw(Diagram diagram, Rectangle drawBounds)

at SoftwareIdeasModeler.SimDiagramControl.canvas_Paint(Object sender, PaintEventArgs e)

at System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)

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

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

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

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