### 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
ProjectSettings *ps = ProjectSettings::get_singleton();
	PackedStringArray enabled_plugins = ps->get("editor_plugins/enabled");
	for (int i = 0; i < enabled_plugins.size(); ++i) {
		if (enabled_plugins.get(i) == p_name) {
			enabled_plugins.remove_at(i);
			break;
		}
	}
	ps->set("editor_plugins/enabled", enabled_plugins);
}
void EditorNode::_plugin_over_edit(EditorPlugin *p_plugin, Object *p_object) {
	if (p_object) {
		editor_plugins_over->add_plugin(p_plugin);
		p_plugin->make_visible(true);
		p_plugin->edit(p_object);
	} else {
		editor_plugins_over->remove_plugin(p_plugin);
		p_plugin->make_visible(false);
		p_plugin->edit(nullptr);
	}
}
void EditorNode::_resources_changed(const Vector<String> &p_resources) {