### 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
List<String> scenes;
	int current_tab = scene_tabs->get_current_tab();
	for (int i = 0; i < p_resources.size(); i++) {
		String file_type = ResourceLoader::get_resource_type(p_resources[i]);
		if (file_type == "PackedScene") {
			scenes.push_back(p_resources[i]);
			
			continue;
		}
		if (!ResourceCache::has(p_resources[i])) {
			
			continue;
		}
		
		Ref<Resource> resource = ResourceCache::get_ref(p_resources[i]);
		if (resource.is_valid()) {
			resource->reload_from_file();
		}
	}
	for (const String &E : scenes) {
		reload_scene(E);
		reload_instances_with_path_in_edited_scenes(E);
	}
	scene_tabs->set_current_tab(current_tab);
}
void EditorNode::_sources_changed(bool p_exist) {