Fix #7635: Game crash on exit scenario editor.

[stormcone]

I think the GM_NORMAL is the only game mode when the station building widgets are available.

[LordAro]

Pretty sure this is good, but I wonder if it's complete - there are a lot of other references to != GM_EDITOR (in road_gui.cpp) that probably should be == GM_NORMAL instead
(this is the correct solution - see road_gui.cpp:722 for where the toolbar is created)

[stormcone]

I think most of them could be == GM_NORMAL. The question is whether we want to narrow the possible game modes from != GM_EDITOR to == GM_NORMAL.

The actual problem here is that the _game_mode is set to GM_MENU before the windows are destroyed:

OpenTTD/src/openttd.cpp

Lines 322 to 329 in 425cd3e

	static void LoadIntroGame(bool load_newgrfs = true)
	{
	_game_mode = GM_MENU;
	if (load_newgrfs) ResetGRFConfig(false);
	/* Setup main window */
	ResetWindowSystem();

I checked the ResetGRFConfig and the ResetWindowSystem functions (and those they call) and I think it would be safe to put the _game_mode = GM_MENU; after the ResetWindowSystem();, because those functions do not depend on the game mode. So that could be an alternative solution.

[LordAro]

This has been open way too long, this will do perfectly fine.