### 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 (p_editing_owner) {
		const ObjectID id = p_editing_owner->get_instance_id();
		for (EditorPlugin *plugin : active_plugins[id]) {
			_plugin_over_edit(plugin, nullptr);
		}
		active_plugins.erase(id);
	} else {
		
		
		List<ObjectID> to_remove;
		for (KeyValue<ObjectID, HashSet<EditorPlugin *>> &kv : active_plugins) {
			if (!ObjectDB::get_instance(kv.key)) {
				to_remove.push_back(kv.key);
				for (EditorPlugin *plugin : kv.value) {
					_plugin_over_edit(plugin, nullptr);
				}
			}
		}
		for (const ObjectID &id : to_remove) {
			active_plugins.erase(id);
		}
	}
}
static bool overrides_external_editor(Object *p_object) {