### 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
editor_export = memnew(EditorExport);
	add_child(editor_export);
	
	EditorColorMap::create();
	theme = create_custom_theme();
	DisplayServer::set_early_window_clear_color_override(true, theme->get_color(SNAME("background"), SNAME("Editor")));
	register_exporters();
	EDITOR_DEF("interface/editor/save_on_focus_loss", false);
	EDITOR_DEF("interface/editor/show_update_spinner", false);
	EDITOR_DEF("interface/editor/update_continuously", false);
	EDITOR_DEF("interface/editor/localize_settings", true);
	EDITOR_DEF_RST("interface/scene_tabs/restore_scenes_on_load", true);
	EDITOR_DEF_RST("interface/inspector/default_property_name_style", EditorPropertyNameProcessor::STYLE_CAPITALIZED);
	EditorSettings::get_singleton()->add_property_hint(PropertyInfo(Variant::INT, "interface/inspector/default_property_name_style", PROPERTY_HINT_ENUM, "Raw,Capitalized,Localized"));
	EDITOR_DEF_RST("interface/inspector/default_float_step", 0.001);
	
	
	EditorSettings::get_singleton()->add_property_hint(PropertyInfo(Variant::FLOAT, "interface/inspector/default_float_step", PROPERTY_HINT_RANGE, "0.0000001,1,0.0000001"));
	EDITOR_DEF_RST("interface/inspector/disable_folding", false);
	EDITOR_DEF_RST("interface/inspector/auto_unfold_foreign_scenes", true);
	EDITOR_DEF("interface/inspector/horizontal_vector2_editing", false);
	EDITOR_DEF("interface/inspector/horizontal_vector_types_editing", true);
	EDITOR_DEF("interface/inspector/open_resources_in_current_inspector", true);
	PackedStringArray open_in_new_inspector_defaults;
	
	open_in_new_inspector_defaults.push_back("Script");
	
	open_in_new_inspector_defaults.push_back("MeshLibrary");
	EDITOR_DEF("interface/inspector/resources_to_open_in_new_inspector", open_in_new_inspector_defaults);
	EDITOR_DEF("interface/inspector/default_color_picker_mode", 0);