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/object/ObjectRepository.cpp

@@ -698,17 +698,17 @@ private:
     }
 };
 
-static std::unique_ptr<ObjectRepository> _objectRepository;
+static ObjectRepository * _objectRepository = nullptr;
 
 IObjectRepository * CreateObjectRepository(IPlatformEnvironment * env)
 {
-    _objectRepository = std::unique_ptr<ObjectRepository>(new ObjectRepository(env));
-    return _objectRepository.get();
+    _objectRepository = new ObjectRepository(env);
+    return _objectRepository;
 }
 
 IObjectRepository * GetObjectRepository()
 {
-    return _objectRepository.get();
+    return _objectRepository;
 }
 
 bool IsObjectCustom(const ObjectRepositoryItem * object)