### 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 (update_spinner_step >= 8) {
					update_spinner_step = 0;
				}
				update_spinner_step_msec = tick;
				update_spinner_step_frame = frame + 1;
				
				if (EDITOR_GET("interface/editor/show_update_spinner")) {
					update_spinner->set_icon(gui_base->get_theme_icon("Progress" + itos(update_spinner_step + 1), SNAME("EditorIcons")));
				}
			}
			editor_selection->update();
			ResourceImporterTexture::get_singleton()->update_imports();
			if (settings_changed) {
				_update_title();
			}
			if (settings_changed) {
				_update_from_settings();
				settings_changed = false;
				emit_signal(SNAME("project_settings_changed"));
			}
			ResourceImporterTexture::get_singleton()->update_imports();
			bottom_panel_updating = false;
		} break;
		case NOTIFICATION_ENTER_TREE: {
			get_tree()->set_disable_node_threading(true); 
			Engine::get_singleton()->set_editor_hint(true);
			Window *window = get_window();
			if (window) {
				
				window->connect("titlebar_changed", callable_mp(this, &EditorNode::_titlebar_resized));