### 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
scene_tabs->connect("tab_close_pressed", callable_mp(this, &EditorNode::_scene_tab_closed).bind(SCENE_TAB_CLOSE));
	scene_tabs->connect("tab_hovered", callable_mp(this, &EditorNode::_scene_tab_hovered));
	scene_tabs->connect("mouse_exited", callable_mp(this, &EditorNode::_scene_tab_exit));
	scene_tabs->connect("gui_input", callable_mp(this, &EditorNode::_scene_tab_input));
	scene_tabs->connect("active_tab_rearranged", callable_mp(this, &EditorNode::_reposition_active_tab));
	scene_tabs->connect("resized", callable_mp(this, &EditorNode::_update_scene_tabs));
	scene_tabs->set_h_size_flags(Control::SIZE_EXPAND_FILL);
	tabbar_container->add_child(scene_tabs);
	scene_tabs_context_menu = memnew(PopupMenu);
	tabbar_container->add_child(scene_tabs_context_menu);
	scene_tabs_context_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
	scene_tab_add = memnew(Button);
	scene_tab_add->set_flat(true);
	scene_tab_add->set_tooltip_text(TTR("Add a new scene."));
	scene_tab_add->set_icon(gui_base->get_theme_icon(SNAME("Add"), SNAME("EditorIcons")));
	scene_tab_add->add_theme_color_override("icon_normal_color", Color(0.6f, 0.6f, 0.6f, 0.8f));
	scene_tabs->add_child(scene_tab_add);
	scene_tab_add->connect("pressed", callable_mp(this, &EditorNode::_menu_option).bind(FILE_NEW_SCENE));
	scene_tab_add_ph = memnew(Control);
	scene_tab_add_ph->set_mouse_filter(Control::MOUSE_FILTER_IGNORE);
	scene_tab_add_ph->set_custom_minimum_size(scene_tab_add->get_minimum_size());
	tabbar_container->add_child(scene_tab_add_ph);
	distraction_free = memnew(Button);
	distraction_free->set_flat(true);
	ED_SHORTCUT_AND_COMMAND("editor/distraction_free_mode", TTR("Distraction Free Mode"), KeyModifierMask::CTRL | KeyModifierMask::SHIFT | Key::F11);
	ED_SHORTCUT_OVERRIDE("editor/distraction_free_mode", "macos", KeyModifierMask::META | KeyModifierMask::CTRL | Key::D);
	distraction_free->set_shortcut(ED_GET_SHORTCUT("editor/distraction_free_mode"));
	distraction_free->set_tooltip_text(TTR("Toggle distraction-free mode."));
	distraction_free->connect("pressed", callable_mp(this, &EditorNode::_toggle_distraction_free_mode));
	distraction_free->set_icon(gui_base->get_theme_icon(SNAME("DistractionFree"), SNAME("EditorIcons")));