### 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 "editor/import/dynamic_font_import_settings.h"
#include "editor/import/editor_import_collada.h"
#include "editor/import/resource_importer_bitmask.h"
#include "editor/import/resource_importer_bmfont.h"
#include "editor/import/resource_importer_csv_translation.h"
#include "editor/import/resource_importer_dynamic_font.h"
#include "editor/import/resource_importer_image.h"
#include "editor/import/resource_importer_imagefont.h"
#include "editor/import/resource_importer_layered_texture.h"
#include "editor/import/resource_importer_obj.h"
#include "editor/import/resource_importer_shader_file.h"
#include "editor/import/resource_importer_texture.h"
#include "editor/import/resource_importer_texture_atlas.h"
#include "editor/import/resource_importer_wav.h"
#include "editor/import/scene_import_settings.h"
#include "editor/import_dock.h"
#include "editor/inspector_dock.h"
#include "editor/multi_node_edit.h"
#include "editor/node_dock.h"
#include "editor/plugin_config_dialog.h"
#include "editor/plugins/animation_player_editor_plugin.h"
#include "editor/plugins/asset_library_editor_plugin.h"
#include "editor/plugins/canvas_item_editor_plugin.h"
#include "editor/plugins/debugger_editor_plugin.h"
#include "editor/plugins/dedicated_server_export_plugin.h"
#include "editor/plugins/editor_preview_plugins.h"
#include "editor/plugins/editor_resource_conversion_plugin.h"
#include "editor/plugins/gdextension_export_plugin.h"
#include "editor/plugins/material_editor_plugin.h"
#include "editor/plugins/mesh_library_editor_plugin.h"