Crash when deleting stop (r6336)

[Train-catcher]

I found this bug much time ago, but just yet I could find a way to reproduce it easily.

So, to reproduce it:
1) plop some stops (or, maybe, you have any stops yet);
2) Open a map and enable "status" info tab (you will see yellow/green/etc circles on the map);
3) Try to delete one of these stops (but ensure, that this stop is highlighted on the map).
4) When delete the last piece of the stop, the game will go crash.

This also does the same effect with "service" info tab, and maybe with some other tabs.

[Dwachs]

Thanks for the useful report! It should be fixed in r6337.