Lua: pop the metatable we created off the stack

[brakhane]

Lua 5.4 crashes without this, given enough calls to Register()

And I can also get 5.3 to crash if I loop 10 times around

WickedEngine/WickedEngine/wiScene_BindLua.cpp

Lines 475 to 501 in 1bec956

	Luna<Scene_BindLua>::Register(L);
	Luna<NameComponent_BindLua>::Register(L);
	Luna<LayerComponent_BindLua>::Register(L);
	Luna<TransformComponent_BindLua>::Register(L);
	Luna<CameraComponent_BindLua>::Register(L);
	Luna<AnimationComponent_BindLua>::Register(L);
	Luna<MaterialComponent_BindLua>::Register(L);
	Luna<MeshComponent_BindLua>::Register(L);
	Luna<EmitterComponent_BindLua>::Register(L);
	Luna<HairParticleSystem_BindLua>::Register(L);
	Luna<LightComponent_BindLua>::Register(L);
	Luna<ObjectComponent_BindLua>::Register(L);
	Luna<InverseKinematicsComponent_BindLua>::Register(L);
	Luna<SpringComponent_BindLua>::Register(L);
	Luna<ScriptComponent_BindLua>::Register(L);
	Luna<RigidBodyPhysicsComponent_BindLua>::Register(L);
	Luna<SoftBodyPhysicsComponent_BindLua>::Register(L);
	Luna<ForceFieldComponent_BindLua>::Register(L);
	Luna<Weather_OceanParams_BindLua>::Register(L);
	Luna<Weather_AtmosphereParams_BindLua>::Register(L);
	Luna<Weather_VolumetricCloudParams_BindLua>::Register(L);
	Luna<WeatherComponent_BindLua>::Register(L);
	Luna<SoundComponent_BindLua>::Register(L);
	Luna<ColliderComponent_BindLua>::Register(L);
	Luna<ExpressionComponent_BindLua>::Register(L);
	Luna<HumanoidComponent_BindLua>::Register(L);
	Luna<DecalComponent_BindLua>::Register(L);

without this patch applies. With this patch, it doesn't crash

[turanszkij]

Thanks!