Thrown when there is only one region in the collection.
Remarks
Removing an AlignmentRegion merges it with the previous region and eliminates any transition between them.
Removing an AlignmentRegion may invalidate references to AlignmentTransition objects. Therefore, any references to an AlignmentTransition should not be used.
Removing an AlignmentRegion may invalidate references to other AlignmentRegion objects in the same collection; therefore, any references held to an AlignmentRegion should not be used.