This seems to be a catchall value passed from brackets-shell, so this is ok.

This `switch` statement should also have a `default:` statement. Text sent to console is basically the same as ERR_UNKNOWN case, but add actual value to make it slightly different, which *may* help us isolate certain problems:

```
    console.error("addMenu(): Unknown Error (" + err + ") when adding the menu " + id);
```