### 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
DisplayServer::get_singleton()->cursor_set_custom_image(Ref<Resource>());
	}
	singleton = this;
	EditorUndoRedoManager::get_singleton()->connect("version_changed", callable_mp(this, &EditorNode::_update_undo_redo_allowed));
	EditorUndoRedoManager::get_singleton()->connect("history_changed", callable_mp(this, &EditorNode::_update_undo_redo_allowed));
	TranslationServer::get_singleton()->set_enabled(false);
	
	if (!EditorSettings::get_singleton()) {
		EditorSettings::create();
	}
	FileAccess::set_backup_save(EDITOR_GET("filesystem/on_save/safe_save_on_backup_then_rename"));
	{
		int display_scale = EDITOR_GET("interface/editor/display_scale");
		switch (display_scale) {
			case 0:
				
				EditorScale::set_scale(EditorSettings::get_singleton()->get_auto_display_scale());
				break;
			case 1:
				EditorScale::set_scale(0.75);
				break;
			case 2:
				EditorScale::set_scale(1.0);
				break;
			case 3:
				EditorScale::set_scale(1.25);
				break;
			case 4:
				EditorScale::set_scale(1.5);
				break;