### Godot version

4.1.3 stable.arch_linux

### System information

Artix Linux Godot v4.1.3 stable.arch_linux

### Issue description

![2023-11-14T16:29:28,788232528+01:00](https://github.com/godotengine/godot/assets/92468390/a79027e2-1539-4ca9-9369-978c32dea26d)
Both "Target Surface:" and "Source Mesh:" accept non Node3D nodes which doesn't really make any sense as they need 3D geometry to function.

### Steps to reproduce

1. Add a MultiMeshInstance3D
2. Add a Node that doesn't inherit Node3D
3. Open the "Populate Surface" menu and click the right button of either "Target Surface:" or "Source Mesh:"

### Minimal reproduction project

N/A
NodePath path = node->get_path_to(get_node(p_path));
	if (browsing_source) {
		mesh_source->set_text(path);
	} else {
		surface_source->set_text(path);
	}
}
void MultiMeshEditor::_menu_option(int p_option) {
	switch (p_option) {
		case MENU_OPTION_POPULATE: {
			if (_last_pp_node != node) {
				surface_source->set_text("..");
				mesh_source->set_text("..");
				populate_axis->select(1);
				populate_rotate_random->set_value(0);
				populate_tilt_random->set_value(0);
				populate_scale_random->set_value(0);
				populate_scale->set_value(1);
				populate_amount->set_value(128);
				_last_pp_node = node;
			}
			populate_dialog->popup_centered(Size2(250, 380));
		} break;
	}
}
void MultiMeshEditor::edit(MultiMeshInstance3D *p_multimesh) {