QAction::setData() always emits changed() even without actual data change.
Original code lacks a guard to check if the data changes.
According to http://doc.qt.io/qt-4.8/signalsandslots.html,
adding guard also benefits to prevent infinite looping in case
of cyclic connections.
Task-number: QTBUG-62006
Change-Id: I776369b668082f9f02e4502a36b1ae234ee7e079
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
7e7683cabb