fix(editor): Esc takes back what a drag did

Esc in the middle of dragging a point of a track kept the moved point,
and the hint said so; dragging a straight was taken back but left an
empty step in the history; a vertex or the radius grip of a curve stayed
moved in the design. Now Esc puts back what was there before the drag in
all three, and the history doesn't keep a step for it.

application/editormoderoute.cpp

@@ -1102,6 +1102,8 @@ void editor_mode::render_route_gizmo()
 		}
 		return;
 	}
+	if (false == m_route_dragging)
+		m_route_drag_from = route.design;
 	m_route_dragging = true;
 	if (grip)
 	{