Sdk/PhysicsSystem: Fix GetWorld() not initializing the internal world

SDK/include/NDK/Systems/PhysicsSystem.hpp

@@ -27,12 +27,13 @@ namespace Ndk
 			static SystemIndex systemIndex;
 
 		private:
+			void CreatePhysWorld() const;
 			void OnEntityValidation(Entity* entity, bool justAdded) override;
 			void OnUpdate(float elapsedTime) override;
 
 			EntityList m_dynamicObjects;
 			EntityList m_staticObjects;
-			std::unique_ptr<Nz::PhysWorld> m_world; ///TODO: std::optional (Should I make a Nz::Optional class?)
+			mutable std::unique_ptr<Nz::PhysWorld> m_world; ///TODO: std::optional (Should I make a Nz::Optional class?)
 	};
 }
 

SDK/include/NDK/Systems/PhysicsSystem.inl

@@ -11,6 +11,9 @@ namespace Ndk
 
 	inline Nz::PhysWorld& PhysicsSystem::GetWorld()
 	{
+		if (!m_world)
+			CreatePhysWorld();
+
 		return *m_world;
 	}
 
@@ -21,6 +24,9 @@ namespace Ndk
 
 	inline const Nz::PhysWorld& PhysicsSystem::GetWorld() const
 	{
+		if (!m_world)
+			CreatePhysWorld();
+
 		return *m_world;
 	}
 }