Fix profiler page navigation

[jw3]

Explicitly declare the _unsaved_changes event on the profiler page to satisfy events.py introspection

Closes #940

[jw3]

The fix addresses the check

        if hasattr(self, '__events__'):
            if name not in self.__events__:
                raise EventsException("Event '%s' is not declared" % name)

[jw3]

ref #921