### 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
pick_main_scene->set_meta("from_native", p_from_native); 
	String main_scene = GLOBAL_GET("application/run/main_scene");
	if (main_scene.is_empty()) {
		current_menu_option = -1;
		pick_main_scene->set_text(TTR("No main scene has ever been defined, select one?\nYou can change it later in \"Project Settings\" under the 'application' category."));
		pick_main_scene->popup_centered();
		if (editor_data.get_edited_scene_root()) {
			select_current_scene_button->set_disabled(false);
			select_current_scene_button->grab_focus();
		} else {
			select_current_scene_button->set_disabled(true);
		}
		return false;
	}
	if (!FileAccess::exists(main_scene)) {
		current_menu_option = -1;
		pick_main_scene->set_text(vformat(TTR("Selected scene '%s' does not exist, select a valid one?\nYou can change it later in \"Project Settings\" under the 'application' category."), main_scene));
		pick_main_scene->popup_centered();
		return false;
	}
	if (ResourceLoader::get_resource_type(main_scene) != "PackedScene") {
		current_menu_option = -1;
		pick_main_scene->set_text(vformat(TTR("Selected scene '%s' is not a scene file, select a valid one?\nYou can change it later in \"Project Settings\" under the 'application' category."), main_scene));
		pick_main_scene->popup_centered();
		return false;
	}
	return true;
}
void EditorNode::_immediate_dialog_confirmed() {