### 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
for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
					if (editor_data.get_scene_path(i) == p_file && i != scene_idx) {
						same_open_scene = true;
					}
				}
				if (same_open_scene) {
					show_warning(TTR("Can't overwrite scene that is still open!"));
					return;
				}
				save_default_environment();
				_save_scene_with_preview(p_file, scene_idx);
				_add_to_recent_scenes(p_file);
				save_editor_layout_delayed();
				if (scene_idx != -1) {
					_discard_changes();
				}
			}
		} break;
		case FILE_SAVE_AND_RUN: {
			if (file->get_file_mode() == EditorFileDialog::FILE_MODE_SAVE_FILE) {
				save_default_environment();
				_save_scene_with_preview(p_file);
				project_run_bar->play_custom_scene(p_file);
			}
		} break;
		case FILE_SAVE_AND_RUN_MAIN_SCENE: {
			ProjectSettings::get_singleton()->set("application/run/main_scene", p_file);
			ProjectSettings::get_singleton()->save();
			if (file->get_file_mode() == EditorFileDialog::FILE_MODE_SAVE_FILE) {
				save_default_environment();