Fix premature deletion of dependencies (#5952)

In particular, the object repository can potentially be deleted before the object manager is deleted. This causes a crash when the object manager is deleted because it requires the object repository within the destructor.

src/openrct2/ride/TrackDesignRepository.cpp

@@ -456,17 +456,17 @@ public:
     }
 };
 
-static std::unique_ptr<TrackDesignRepository> _trackDesignRepository;
+static TrackDesignRepository * _trackDesignRepository = nullptr;
 
 ITrackDesignRepository * CreateTrackDesignRepository(IPlatformEnvironment * env)
 {
-    _trackDesignRepository = std::unique_ptr<TrackDesignRepository>(new TrackDesignRepository(env));
-    return _trackDesignRepository.get();
+    _trackDesignRepository = new TrackDesignRepository(env);
+    return _trackDesignRepository;
 }
 
 ITrackDesignRepository * GetTrackDesignRepository()
 {
-    return _trackDesignRepository.get();
+    return _trackDesignRepository;
 }
 
 extern "C"