How to create an invalid QModelIndex?

I am implementing a function which searchs a QModelIndex based on a QString input. However if I cannot find this index, the function should retun an invalid index. My model is a QStandardItemModel.

Is is okay to return invisibleRootItem()->index() as an invalid index? In the qt documentation is noted that it will always creates an invalid index.

You must use the default constructor of QModelIndex(e.g. return QModelIndex()) which is null as indicated in the docs:

QModelIndex::QModelIndex()
Creates a new empty model index. This type of model index is used to indicate that the position in the model is invalid.

_{(emphasis mine)}