### 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
if (InspectorDock::get_inspector_singleton()) {
		InspectorDock::get_inspector_singleton()->update_tree();
	}
}
void EditorNode::_editor_select_next() {
	int editor = _get_current_main_editor();
	do {
		if (editor == editor_table.size() - 1) {
			editor = 0;
		} else {
			editor++;
		}
	} while (!main_editor_buttons[editor]->is_visible());
	editor_select(editor);
}
void EditorNode::_open_command_palette() {
	command_palette->open_popup();
}
void EditorNode::_editor_select_prev() {
	int editor = _get_current_main_editor();
	do {
		if (editor == 0) {
			editor = editor_table.size() - 1;
		} else {
			editor--;
		}
	} while (!main_editor_buttons[editor]->is_visible());
	editor_select(editor);
}
Error EditorNode::load_resource(const String &p_resource, bool p_ignore_broken_deps) {