No need to insert empty ```QVariantList``` instances here - from http://qt-project.org/doc/qt-5.0/qtcore/qmap.html#operator-5b-5d:

<q>If the map contains no item with key key, the function inserts a default-constructed value into the map with key key, and returns a reference to it.</q>

If you don't have any users, it will still work, as the outside code using QMap will also create the empty ```QVariantList``` if accessed using ```operator[]```. The only thing to be careful about is that things like ```contains()``` will behave differently in that case (as the key is never created).