### 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
FileSystemDock::get_singleton()->set_file_sort(dock_filesystem_file_sort);
	}
	if (p_layout->has_section_key(p_section, "dock_filesystem_file_list_display_mode")) {
		FileSystemDock::FileListDisplayMode dock_filesystem_file_list_display_mode = FileSystemDock::FileListDisplayMode(int(p_layout->get_value(p_section, "dock_filesystem_file_list_display_mode")));
		FileSystemDock::get_singleton()->set_file_list_display_mode(dock_filesystem_file_list_display_mode);
	}
	if (p_layout->has_section_key(p_section, "dock_filesystem_selected_paths")) {
		PackedStringArray dock_filesystem_selected_paths = p_layout->get_value(p_section, "dock_filesystem_selected_paths");
		for (int i = 0; i < dock_filesystem_selected_paths.size(); i++) {
			FileSystemDock::get_singleton()->select_file(dock_filesystem_selected_paths[i]);
		}
	}
	
	PackedStringArray uncollapsed_tis;
	if (p_layout->has_section_key(p_section, "dock_filesystem_uncollapsed_paths")) {
		uncollapsed_tis = p_layout->get_value(p_section, "dock_filesystem_uncollapsed_paths");
	} else {
		uncollapsed_tis = { "res:" };
	}
	if (!uncollapsed_tis.is_empty()) {
		for (int i = 0; i < uncollapsed_tis.size(); i++) {
			TreeItem *uncollapsed_ti = FileSystemDock::get_singleton()->get_tree_control()->get_item_with_metadata(uncollapsed_tis[i], 0);
			if (uncollapsed_ti) {
				uncollapsed_ti->set_collapsed(false);
			}
		}
		FileSystemDock::get_singleton()->get_tree_control()->queue_redraw();
	}
}
void EditorNode::_save_central_editor_layout_to_config(Ref<ConfigFile> p_config_file) {