### 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
Node *scene = editor_data.get_edited_scene_root();
	if (!scene) {
		return;
	}
	List<String> esl;
	p_config_file->get_section_keys("editor_states", &esl);
	Dictionary md;
	for (const String &E : esl) {
		Variant st = p_config_file->get_value("editor_states", E);
		if (st.get_type() != Variant::NIL) {
			md[E] = st;
		}
	}
	editor_data.set_editor_plugin_states(md);
}
void EditorNode::_save_editor_states(const String &p_file, int p_idx) {