Fix Crash On Close When 3D Is Disabled

(cherry picked from commit fc65cc64b92d1663cf858f3c6cf4f039c2da67e8)

scene/register_scene_types.cpp

@@ -762,7 +762,11 @@ void unregister_scene_types() {
 	ResourceLoader::remove_resource_format_loader(resource_loader_bmfont);
 	resource_loader_bmfont.unref();
 
+	//SpatialMaterial is not initialised when 3D is disabled, so it shouldn't be cleaned up either
+#ifndef _3D_DISABLED
 	SpatialMaterial::finish_shaders();
+#endif // _3D_DISABLED
+
 	ParticlesMaterial::finish_shaders();
 	CanvasItemMaterial::finish_shaders();
 	SceneStringNames::free();