### 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 (p_error) {
		switch (p_error) {
			case ERR_CANT_OPEN: {
				show_accept(vformat(TTR("Can't open file '%s'. The file could have been moved or deleted."), p_file.get_file()), TTR("OK"));
			} break;
			case ERR_PARSE_ERROR: {
				show_accept(vformat(TTR("Error while parsing file '%s'."), p_file.get_file()), TTR("OK"));
			} break;
			case ERR_FILE_CORRUPT: {
				show_accept(vformat(TTR("Scene file '%s' appears to be invalid/corrupt."), p_file.get_file()), TTR("OK"));
			} break;
			case ERR_FILE_NOT_FOUND: {
				show_accept(vformat(TTR("Missing file '%s' or one of its dependencies."), p_file.get_file()), TTR("OK"));
			} break;
			default: {
				show_accept(vformat(TTR("Error while loading file '%s'."), p_file.get_file()), TTR("OK"));
			} break;
		}
	}
}
void EditorNode::_load_editor_plugin_states_from_config(const Ref<ConfigFile> &p_config_file) {