QML crashes when value of property becomes NaN

Our application displays data send by backend that we do not control.

We have encountered a crash when the data contains a specific value that should be interpreted as NaN. I have created a small example that demonstrates the issue.

On Qt 5.6.2 (used in production) the output is:

returning:  42
qml: changing
returning:  nan
Segmentation fault (core dumped)

On Qt 5.9.3 the output is:

returning:  42
qml: changing
returning:  nan
file:///.../qmldoublecrash/Test.qml:11:28: Unable to assign QJSValue to double

Both behaviors are not acceptable, because the value change cannot be processed in QML.

Please provide fixes for both 5.6 and 5.9.