### Godot version

4.1 rc3

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

This™
![image](https://github.com/godotengine/godot/assets/2223172/cb33110f-a5b0-400a-951f-3fa425f05714)

It can still happen, but it's more difficult to trigger.

### Steps to reproduce

1. Create a new scene with a Control node
2. Add Theme to the Control
3. Open Theme Editor
4. Clear the `theme` property in Control
5. Save, with Theme Editor opened
6. Restart

### Minimal reproduction project

N/A
settings_menu->add_item(TTR("Open Editor Settings Folder"), SETTINGS_EDITOR_CONFIG_FOLDER);
	}
	settings_menu->add_separator();
#endif
	settings_menu->add_item(TTR("Manage Editor Features..."), SETTINGS_MANAGE_FEATURE_PROFILES);
#ifndef ANDROID_ENABLED
	settings_menu->add_item(TTR("Manage Export Templates..."), SETTINGS_MANAGE_EXPORT_TEMPLATES);
#endif
#if !defined(ANDROID_ENABLED) && !defined(WEB_ENABLED)
	settings_menu->add_item(TTR("Configure FBX Importer..."), SETTINGS_MANAGE_FBX_IMPORTER);
#endif
	help_menu = memnew(PopupMenu);
	help_menu->set_name(TTR("Help"));
	main_menu->add_child(help_menu);
	help_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
	ED_SHORTCUT_AND_COMMAND("editor/editor_help", TTR("Search Help"), Key::F1);
	ED_SHORTCUT_OVERRIDE("editor/editor_help", "macos", KeyModifierMask::ALT | Key::SPACE);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("HelpSearch"), SNAME("EditorIcons")), ED_GET_SHORTCUT("editor/editor_help"), HELP_SEARCH);
	help_menu->add_separator();
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/online_docs", TTR("Online Documentation")), HELP_DOCS);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/q&a", TTR("Questions & Answers")), HELP_QA);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/report_a_bug", TTR("Report a Bug")), HELP_REPORT_A_BUG);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ActionCopy"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/copy_system_info", TTR("Copy System Info")), HELP_COPY_SYSTEM_INFO);
	help_menu->set_item_tooltip(-1, TTR("Copies the system info as a single-line text into the clipboard."));
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/suggest_a_feature", TTR("Suggest a Feature")), HELP_SUGGEST_A_FEATURE);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/send_docs_feedback", TTR("Send Docs Feedback")), HELP_SEND_DOCS_FEEDBACK);
	help_menu->add_icon_shortcut(gui_base->get_theme_icon(SNAME("ExternalLink"), SNAME("EditorIcons")), ED_SHORTCUT_AND_COMMAND("editor/community", TTR("Community")), HELP_COMMUNITY);
	help_menu->add_separator();
	if (!global_menu || !OS::get_singleton()->has_feature("macos")) {