### 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
#include "scene/gui/link_button.h"
#include "scene/gui/menu_bar.h"
#include "scene/gui/menu_button.h"
#include "scene/gui/panel.h"
#include "scene/gui/panel_container.h"
#include "scene/gui/popup.h"
#include "scene/gui/rich_text_label.h"
#include "scene/gui/split_container.h"
#include "scene/gui/tab_bar.h"
#include "scene/gui/tab_container.h"
#include "scene/main/window.h"
#include "scene/property_utils.h"
#include "scene/resources/image_texture.h"
#include "scene/resources/packed_scene.h"
#include "scene/resources/portable_compressed_texture.h"
#include "servers/display_server.h"
#include "servers/navigation_server_3d.h"
#include "servers/physics_server_2d.h"
#include "editor/audio_stream_preview.h"
#include "editor/debugger/editor_debugger_node.h"
#include "editor/debugger/script_editor_debugger.h"
#include "editor/dependency_editor.h"
#include "editor/editor_about.h"
#include "editor/editor_audio_buses.h"
#include "editor/editor_build_profile.h"
#include "editor/editor_command_palette.h"
#include "editor/editor_data.h"
#include "editor/editor_feature_profile.h"
#include "editor/editor_folding.h"
#include "editor/editor_help.h"