### 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
if (singleton->exiting) {
		return;
	}
	ERR_FAIL_COND_MSG(!singleton->editor_data.has_extension_editor_plugin(p_class_name), vformat("No editor plugin added for class: %s", p_class_name));
	EditorPlugin *plugin = singleton->editor_data.get_extension_editor_plugin(p_class_name);
	remove_editor_plugin(plugin);
	memfree(plugin);
	singleton->editor_data.remove_extension_editor_plugin(p_class_name);
}
void EditorNode::_update_addon_config() {
	if (_initializing_plugins) {
		return;
	}
	Vector<String> enabled_addons;
	for (const KeyValue<String, EditorPlugin *> &E : addon_name_to_plugin) {
		enabled_addons.push_back(E.key);
	}
	if (enabled_addons.size() == 0) {
		ProjectSettings::get_singleton()->set("editor_plugins/enabled", Variant());
	} else {
		enabled_addons.sort();
		ProjectSettings::get_singleton()->set("editor_plugins/enabled", enabled_addons);
	}
	project_settings_editor->queue_save();
}
void EditorNode::set_addon_plugin_enabled(const String &p_addon, bool p_enabled, bool p_config_changed) {