### 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
for (FileDialog *E : file_dialogs) {
		E->invalidate();
	}
	for (EditorFileDialog *E : editor_file_dialogs) {
		E->invalidate();
	}
	_mark_unsaved_scenes();
	
	String export_error;
	Error err = OK;
	if (!export_defer.preset.is_empty() && !EditorFileSystem::get_singleton()->is_scanning()) {
		String preset_name = export_defer.preset;
		
		
		export_defer.preset = "";
		Ref<EditorExportPreset> export_preset;
		for (int i = 0; i < EditorExport::get_singleton()->get_export_preset_count(); ++i) {
			export_preset = EditorExport::get_singleton()->get_export_preset(i);
			if (export_preset->get_name() == preset_name) {
				break;
			}
			export_preset.unref();