### 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/editor_inspector.h"
#include "editor/editor_interface.h"
#include "editor/editor_layouts_dialog.h"
#include "editor/editor_log.h"
#include "editor/editor_native_shader_source_visualizer.h"
#include "editor/editor_paths.h"
#include "editor/editor_plugin.h"
#include "editor/editor_properties.h"
#include "editor/editor_property_name_processor.h"
#include "editor/editor_quick_open.h"
#include "editor/editor_resource_preview.h"
#include "editor/editor_run.h"
#include "editor/editor_run_native.h"
#include "editor/editor_scale.h"
#include "editor/editor_settings.h"
#include "editor/editor_settings_dialog.h"
#include "editor/editor_themes.h"
#include "editor/editor_translation_parser.h"
#include "editor/editor_undo_redo_manager.h"
#include "editor/export/editor_export.h"
#include "editor/export/export_template_manager.h"
#include "editor/export/project_export.h"
#include "editor/fbx_importer_manager.h"
#include "editor/filesystem_dock.h"
#include "editor/gui/editor_file_dialog.h"
#include "editor/gui/editor_run_bar.h"
#include "editor/gui/editor_title_bar.h"
#include "editor/gui/editor_toaster.h"
#include "editor/history_dock.h"
#include "editor/import/audio_stream_import_settings.h"