### 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
resource_conversion_plugins.push_back(orm_mat_convert);
		Ref<CanvasItemMaterialConversionPlugin> canvas_item_mat_convert;
		canvas_item_mat_convert.instantiate();
		resource_conversion_plugins.push_back(canvas_item_mat_convert);
		Ref<ParticleProcessMaterialConversionPlugin> particles_mat_convert;
		particles_mat_convert.instantiate();
		resource_conversion_plugins.push_back(particles_mat_convert);
		Ref<ProceduralSkyMaterialConversionPlugin> procedural_sky_mat_convert;
		procedural_sky_mat_convert.instantiate();
		resource_conversion_plugins.push_back(procedural_sky_mat_convert);
		Ref<PanoramaSkyMaterialConversionPlugin> panorama_sky_mat_convert;
		panorama_sky_mat_convert.instantiate();
		resource_conversion_plugins.push_back(panorama_sky_mat_convert);
		Ref<PhysicalSkyMaterialConversionPlugin> physical_sky_mat_convert;
		physical_sky_mat_convert.instantiate();
		resource_conversion_plugins.push_back(physical_sky_mat_convert);
		Ref<FogMaterialConversionPlugin> fog_mat_convert;
		fog_mat_convert.instantiate();
		resource_conversion_plugins.push_back(fog_mat_convert);
		Ref<VisualShaderConversionPlugin> vshader_convert;
		vshader_convert.instantiate();
		resource_conversion_plugins.push_back(vshader_convert);
	}
	update_spinner_step_msec = OS::get_singleton()->get_ticks_msec();
	update_spinner_step_frame = Engine::get_singleton()->get_frames_drawn();
	editor_plugin_screen = nullptr;
	editor_plugins_over = memnew(EditorPluginList);
	editor_plugins_force_over = memnew(EditorPluginList);
	editor_plugins_force_input_forwarding = memnew(EditorPluginList);
	Ref<GDExtensionExportPlugin> gdextension_export_plugin;