'Unable to assign [undefined] to QString' when QML string property is set from Javascript

When running the attached QML in the qtquick2applicationviewer on an ARM platform, the text printed is "Initial" (should be "After completion") and stderr says:

file:///.../qml/QmlTest/main.qml:9:15: Unable to assign [undefined] to QString

On x86_64 with gcc-4.8.1 it works as expected.

There is a somewhat related issue in https://bugreports.qt-project.org/browse/QTBUG-36994. But since I cannot reproduce the described issue. I'm not sure whether it is the same problem.