### 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
save_all_scenes();
	ProjectSettings::get_singleton()->save();
	disk_changed->hide();
}
void EditorNode::_reload_modified_scenes() {
	int current_idx = editor_data.get_edited_scene();
	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (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) {
			String filename = editor_data.get_scene_path(i);
			editor_data.set_edited_scene(i);
			_remove_edited_scene(false);
			Error err = load_scene(filename, false, false, true, false, true);
			if (err != OK) {
				ERR_PRINT(vformat("Failed to load scene: %s", filename));
			}
			editor_data.move_edited_scene_to_index(i);
		}
	}
	set_current_scene(current_idx);
	_update_scene_tabs();
	disk_changed->hide();
}
void EditorNode::_reload_project_settings() {