### 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
disk_changed_list->clear();
	TreeItem *r = disk_changed_list->create_item();
	disk_changed_list->set_hide_root(true);
	bool need_reload = false;
	
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		Ref<DirAccess> da = DirAccess::create(DirAccess::ACCESS_RESOURCES);
		if (editor_data.get_scene_path(i) == "" || !da->file_exists(editor_data.get_scene_path(i))) {
			continue;
		}
		uint64_t last_date = editor_data.get_scene_modified_time(i);
		uint64_t date = FileAccess::get_modified_time(editor_data.get_scene_path(i));
		if (date > last_date) {
			TreeItem *ti = disk_changed_list->create_item(r);
			ti->set_text(0, editor_data.get_scene_path(i).get_file());
			need_reload = true;
		}
	}
	String project_settings_path = ProjectSettings::get_singleton()->get_resource_path().path_join("project.godot");
	if (FileAccess::get_modified_time(project_settings_path) > ProjectSettings::get_singleton()->get_last_saved_time()) {
		TreeItem *ti = disk_changed_list->create_item(r);
		ti->set_text(0, "project.godot");
		need_reload = true;
	}
	if (need_reload) {
		disk_changed->call_deferred(SNAME("popup_centered_ratio"), 0.3);
	}
}
void EditorNode::_resave_scenes(String p_str) {