Access to the Game global instance via g_Game might break Atlas

[Vladislav Belov]

Currently in Atlas we have a single g_Game instance. That means after opening Atlas viewer we might still access it. That might lead to crashes (like #6524) or another undefined behavior.

To solve that properly we need to remove all accesses to global states that might depend on the active game view.

Refs #6524.

[Freagarach]

Pushing back.