### Godot version

v4.2.dev.custom_build [0c2144da9]

### System information

Debian Linux X11 Xfce

### Issue description

Prerequisite: Be in Single Window Mode in the Editor
The Filesystem Dock is unusable when it is floating, which is not expected.
It appears garbled in the top-left corner:
![image](https://github.com/godotengine/godot/assets/6299227/109f7922-97de-44c3-814a-ca7f970e0602)

The following errors are shown:
```
  editor/window_wrapper.cpp:220 - Condition "!is_window_available()" is true.
  editor/window_wrapper.cpp:202 - Condition "!get_window_enabled()" is true. Returning: Rect2i()
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
  editor/window_wrapper.cpp:207 - Condition "!get_window_enabled()" is true. Returning: -1
```

bisecting lead to #62378
possibly related to #44439

### Steps to reproduce

1. Start a project in the Editor
2. Switch to Single Window Mode in the Editor and reload (if necessary)
3. Make the Filesystem Dock floating

### Minimal reproduction project

Editor issue
while (screen_list->get_child_count(false) > 0) {
		Node *child = screen_list->get_child(0);
		screen_list->remove_child(child);
		child->queue_free();
	}
	
	const real_t height = real_t(get_theme_font_size("font_size")) * 1.5;
	int current_screen = get_window()->get_current_screen();
	for (int i = 0; i < DisplayServer::get_singleton()->get_screen_count(); i++) {
		Button *button = memnew(Button);
		Size2 screen_size = Size2(DisplayServer::get_singleton()->screen_get_size(i));
		Size2 button_size = Size2(height * (screen_size.x / screen_size.y), height);
		button->set_custom_minimum_size(button_size);
		screen_list->add_child(button);
		button->set_text(itos(i));
		button->set_text_alignment(HORIZONTAL_ALIGNMENT_CENTER);
		button->set_tooltip_text(vformat(TTR("Make this panel floating in the screen %d."), i));
		if (i == current_screen) {
			Color accent_color = get_theme_color("accent_color", "Editor");
			button->add_theme_color_override("font_color", accent_color);
		}
		button->connect("pressed", callable_mp(this, &ScreenSelect::_emit_screen_signal).bind(i));
		button->connect("pressed", callable_mp(static_cast<BaseButton *>(this), &ScreenSelect::set_pressed).bind(false));
		button->connect("pressed", callable_mp(static_cast<Window *>(popup), &Popup::hide));
	}
}
void ScreenSelect::_emit_screen_signal(int p_screen_idx) {