controls/SizeGroup: shield against nullptr qmlContext
Stuff goes dramatically wrong if we try to use a QQmlProperty for an item that lacks a qmlContext.
BUG: 435593 FIXED-IN: 5.82
Stuff goes dramatically wrong if we try to use a QQmlProperty for an item that lacks a qmlContext.
BUG: 435593 FIXED-IN: 5.82