### 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
return;
			}
			show_warning(vformat(TTR("Unable to load addon script from path: '%s'. This might be due to a code error in that script.\nDisabling the addon at '%s' to prevent further errors."), script_path, addon_path));
			_remove_plugin_from_enabled(addon_path);
			return;
		}
		
		if (String(scr->get_instance_base_type()) != "EditorPlugin") {
			show_warning(vformat(TTR("Unable to load addon script from path: '%s' Base type is not EditorPlugin."), script_path));
			return;
		}
		if (!scr->is_tool()) {
			show_warning(vformat(TTR("Unable to load addon script from path: '%s' Script is not in tool mode."), script_path));
			return;
		}
	}
	EditorPlugin *ep = memnew(EditorPlugin);
	ep->set_script(scr);
	ep->set_plugin_version(plugin_version);
	addon_name_to_plugin[addon_path] = ep;
	add_editor_plugin(ep, p_config_changed);
	_update_addon_config();
}
bool EditorNode::is_addon_plugin_enabled(const String &p_addon) const {
	if (p_addon.begins_with("res:")) {
		return addon_name_to_plugin.has(p_addon);
	}
	return addon_name_to_plugin.has("res:addons/" + p_addon + "/plugin.cfg");
}
void EditorNode::_remove_edited_scene(bool p_change_tab) {