Selected value is not written back to the model in SQL Widget Mapper Example

Steps to reproduce:

1. Run SQL Widget Mapper Example (https://doc.qt.io/qt-5/qtsql-sqlwidgetmapper-example.html)
2. Press the next button and change the value of the 'Type' field. 
3. Move to next view and click previous.

Actual: Selected type was not stored. See the attached video.

Expected: Selected value should be stored. 

NOTE: It is not stored on macOS only. It works well on Linux and Windows.