/// <summary>
/// Ensures the terminal at one end of a divider has been indexed.
/// </summary>
/// <param name="t">The terminal at the start or end of a divider</param>
/// <param name="cx">The spatial index to add to</param>
static void AddToIndex(ITerminal t, EditingIndex cx)
{
Intersection x = (t as Intersection);
if (x!=null && !x.IsIndexed)
cx.AddIntersection(x);
}
