### 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
Control *v_spacer = memnew(Control);
	version_info_vbc->add_child(v_spacer);
	version_btn = memnew(LinkButton);
	version_btn->set_text(VERSION_FULL_CONFIG);
	String hash = String(VERSION_HASH);
	if (hash.length() != 0) {
		hash = " " + vformat("[%s]", hash.left(9));
	}
	
	version_btn->set_meta(META_TEXT_TO_COPY, "v" VERSION_FULL_BUILD + hash);
	
	version_btn->set_self_modulate(Color(1, 1, 1, 0.65));
	version_btn->set_underline_mode(LinkButton::UNDERLINE_MODE_ON_HOVER);
	version_btn->set_tooltip_text(TTR("Click to copy."));
	version_btn->connect("pressed", callable_mp(this, &EditorNode::_version_button_pressed));
	version_info_vbc->add_child(version_btn);
	
	Control *h_spacer = memnew(Control);
	bottom_panel_hb->add_child(h_spacer);
	bottom_panel_raise = memnew(Button);
	bottom_panel_raise->set_flat(true);
	bottom_panel_raise->set_icon(gui_base->get_theme_icon(SNAME("ExpandBottomDock"), SNAME("EditorIcons")));
	bottom_panel_raise->set_shortcut(ED_SHORTCUT_AND_COMMAND("editor/bottom_panel_expand", TTR("Expand Bottom Panel"), KeyModifierMask::SHIFT | Key::F12));
	bottom_panel_hb->add_child(bottom_panel_raise);
	bottom_panel_raise->hide();
	bottom_panel_raise->set_toggle_mode(true);
	bottom_panel_raise->connect("toggled", callable_mp(this, &EditorNode::_bottom_panel_raise_toggled));
	log = memnew(EditorLog);
	Button *output_button = add_bottom_panel_item(TTR("Output"), log);
	log->set_tool_button(output_button);