### 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
ADD_SIGNAL(MethodInfo("window_visibility_changed", PropertyInfo(Variant::BOOL, "visible")));
	ADD_SIGNAL(MethodInfo("window_close_requested"));
}
void WindowWrapper::_notification(int p_what) {
	if (!is_window_available()) {
		return;
	}
	switch (p_what) {
		case NOTIFICATION_VISIBILITY_CHANGED: {
			if (get_window_enabled() && is_visible()) {
				
				
				window->grab_focus();
			}
		} break;
		case NOTIFICATION_READY: {
			set_process_shortcut_input(true);
		} break;
		case NOTIFICATION_THEME_CHANGED: {
			window_background->add_theme_style_override("panel", get_theme_stylebox("PanelForeground", "EditorStyles"));
		} break;
	}
}
void WindowWrapper::shortcut_input(const Ref<InputEvent> &p_event) {