QML JavaScript crash when deleting property in for-in loop

The following code crashes:

function test() {
    var obj = { 1: null, 2: null, 4096: null }
    for (var t in obj)
        if (t == 2)
            delete obj[t]
    }

For it to crash, the object must have all numeric property names, at least one must be larger than 4095, and a for-in loop must delete one of the properties other than the last. It crashes when it tries to do the next iteration of the loop. It doesn't seem to happen on a Mac.

The only workaround I've found is to include a non-numeric property, and explicitly skip over it in my for-in loop.

This may be related to https://bugreports.qt.io/browse/QTBUG-61356.