QQmlEngine/QJSEngine toScriptValue<QVariantMap> assumes strings for keys

When converting a QVariantMap to a script value using Q[Qml,JS]Engine, the javascript engine assumes that all the keys are strings but still tries to convert the values. As a result if you use a QVariantMap with a number as a key (wrapped in quotes), the engine will convert the value to a js Number and segfault in QV4::InternalClass::addMember on the string lookup. Attached is a small example exhibiting the crash