Only allow MeshInstance3D-inherited nodes in MultiMesh Populate Surface dialog

editor/plugins/multimesh_editor_plugin.cpp

@@ -354,6 +354,9 @@ MultiMeshEditor::MultiMeshEditor() {
 
 	populate_dialog->get_ok_button()->connect("pressed", callable_mp(this, &MultiMeshEditor::_populate));
 	std = memnew(SceneTreeDialog);
+	Vector<StringName> valid_types;
+	valid_types.push_back("MeshInstance3D");
+	std->set_valid_types(valid_types);
 	populate_dialog->add_child(std);
 	std->connect("selected", callable_mp(this, &MultiMeshEditor::_browsed));