Make ParticlesMaterial included with disable_3d=yes option

scene/register_scene_types.cpp

@@ -564,6 +564,9 @@ void register_scene_types() {
 	/* REGISTER RESOURCES */
 
 	ClassDB::register_virtual_class<Shader>();
+	ClassDB::register_class<ParticlesMaterial>();
+	SceneTree::add_idle_callback(ParticlesMaterial::flush_changes);
+	ParticlesMaterial::init_shaders();
 
 #ifndef _3D_DISABLED
 	ClassDB::register_virtual_class<Mesh>();
@@ -581,10 +584,6 @@ void register_scene_types() {
 	SceneTree::add_idle_callback(SpatialMaterial::flush_changes);
 	SpatialMaterial::init_shaders();
 
-	ClassDB::register_class<ParticlesMaterial>();
-	SceneTree::add_idle_callback(ParticlesMaterial::flush_changes);
-	ParticlesMaterial::init_shaders();
-
 	ClassDB::register_class<MultiMesh>();
 	ClassDB::register_class<MeshLibrary>();