### 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
_menu_option_confirm(p_option, false);
}
void EditorNode::_menu_confirm_current() {
	_menu_option_confirm(current_menu_option, true);
}
void EditorNode::_dialog_display_save_error(String p_file, Error p_error) {
	if (p_error) {
		switch (p_error) {
			case ERR_FILE_CANT_WRITE: {
				show_accept(TTR("Can't open file for writing:") + " " + p_file.get_extension(), TTR("OK"));
			} break;
			case ERR_FILE_UNRECOGNIZED: {
				show_accept(TTR("Requested file format unknown:") + " " + p_file.get_extension(), TTR("OK"));
			} break;
			default: {
				show_accept(TTR("Error while saving."), TTR("OK"));
			} break;
		}
	}
}
void EditorNode::_dialog_display_load_error(String p_file, Error p_error) {