When the Topology UI is reloaded it tries to restore the user's previous state, which include the selected topology provider, the vertices in focus, etc...
Restoring the vertices in focus, triggers a graph change, which in turns tries to load the info panel components. However, it is possible that the elements referred to are no longer available (i.e have been removed from the database). This is show in the attached exception.
When this happens, the whole Topology UI fails to load.