Qt Quick Controls 1 TreeView prints Model size error

Since Qt 5.12, when using a Qt Quick Controls 1 TreeView, a debug message is printed on redraw of the view about a model size with a negative number:

Model size of -7 is less than 0
Model size of -8 is less than 0
Model size of -96 is less than 0
Model size of -98 is less than 0

This issue can be reproduced by running the File System Browser Example with Qt 5.12.

The warning does not seem harmful and was introduced by the commit 92b2a4f58d related with the issue QTBUG-54752.

This fix returns an Invalid type and may be related with the issue QTBUG-71789.