This testcase works fine in 5.0.2 but crashes/asserts in 5.2.1 and current 5.3.0.
What is happening is that basically the delegate is being released from the list while a function on that very same delegate is being executed. This causes things to go badly.
In main.qml there is a bigger explanation of what i think is going on.
|For Gerrit Dashboard: QTBUG-37227|
|79857,2||Fix crash when accessing var properties in objects with invalid context||stable||qt/qtdeclarative||Status: MERGED||+2||0|