### 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
int selected_bottom_panel_item_idx = -1;
	for (int i = 0; i < bottom_panel_items.size(); i++) {
		if (bottom_panel_items[i].button->is_pressed()) {
			selected_bottom_panel_item_idx = i;
			break;
		}
	}
	if (selected_bottom_panel_item_idx != -1) {
		p_config_file->set_value(EDITOR_NODE_CONFIG_SECTION, "selected_bottom_panel_item", selected_bottom_panel_item_idx);
	} else {
		p_config_file->set_value(EDITOR_NODE_CONFIG_SECTION, "selected_bottom_panel_item", Variant());
	}
	
	int selected_default_debugger_tab_idx = EditorDebuggerNode::get_singleton()->get_default_debugger()->get_current_debugger_tab();
	p_config_file->set_value(EDITOR_NODE_CONFIG_SECTION, "selected_default_debugger_tab_idx", selected_default_debugger_tab_idx);
	
	int selected_main_editor_idx = -1;
	for (int i = 0; i < main_editor_buttons.size(); i++) {
		if (main_editor_buttons[i]->is_pressed()) {
			selected_main_editor_idx = i;
			break;
		}
	}
	if (selected_main_editor_idx != -1) {
		p_config_file->set_value(EDITOR_NODE_CONFIG_SECTION, "selected_main_editor_idx", selected_main_editor_idx);
	} else {
		p_config_file->set_value(EDITOR_NODE_CONFIG_SECTION, "selected_main_editor_idx", Variant());
	}
}
void EditorNode::_load_central_editor_layout_from_config(Ref<ConfigFile> p_config_file) {