### Godot version

4.x

### System information

Windows 10

### Issue description

The `Search Result` panel is not correctly updated when changing the theme.

https://user-images.githubusercontent.com/66004280/208964493-d0423b78-3418-44c9-95ed-822fd34c4720.mp4



### Steps to reproduce

1. Search something
2. Change the theme

### Minimal reproduction project

--
hbc->add_child(_progress_bar);
		set_progress_visible(false);
		_status_label = memnew(Label);
		hbc->add_child(_status_label);
		_refresh_button = memnew(Button);
		_refresh_button->set_text(TTR("Refresh"));
		_refresh_button->connect("pressed", callable_mp(this, &FindInFilesPanel::_on_refresh_button_clicked));
		_refresh_button->hide();
		hbc->add_child(_refresh_button);
		_cancel_button = memnew(Button);
		_cancel_button->set_text(TTR("Cancel"));
		_cancel_button->connect("pressed", callable_mp(this, &FindInFilesPanel::_on_cancel_button_clicked));
		_cancel_button->hide();
		hbc->add_child(_cancel_button);
		vbc->add_child(hbc);
	}
	_results_display = memnew(Tree);
	_results_display->add_theme_font_override("font", EditorNode::get_singleton()->get_gui_base()->get_theme_font(SNAME("source"), SNAME("EditorFonts")));
	_results_display->add_theme_font_size_override("font_size", EditorNode::get_singleton()->get_gui_base()->get_theme_font_size(SNAME("source_size"), SNAME("EditorFonts")));
	_results_display->set_v_size_flags(SIZE_EXPAND_FILL);
	_results_display->connect("item_selected", callable_mp(this, &FindInFilesPanel::_on_result_selected));
	_results_display->connect("item_edited", callable_mp(this, &FindInFilesPanel::_on_item_edited));
	_results_display->set_hide_root(true);
	_results_display->set_select_mode(Tree::SELECT_ROW);
	_results_display->set_allow_rmb_select(true);
	_results_display->set_allow_reselect(true);
	_results_display->create_item(); 
	vbc->add_child(_results_display);
	{
		_replace_container = memnew(HBoxContainer);