### 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 (!bool(EDITOR_GET("interface/scene_tabs/show_thumbnail_on_hover"))) {
		return;
	}
	int current_tab = scene_tabs->get_current_tab();
	if (p_tab == current_tab || p_tab < 0) {
		tab_preview_panel->hide();
	} else {
		String path = editor_data.get_scene_path(p_tab);
		if (!path.is_empty()) {
			EditorResourcePreview::get_singleton()->queue_resource_preview(path, this, "_thumbnail_done", p_tab);
		}
	}
}
void EditorNode::_scene_tab_exit() {
	tab_preview_panel->hide();
}
void EditorNode::_scene_tab_input(const Ref<InputEvent> &p_input) {