QTree/TableView: Don't emit clicked when releasing after double click

If an item is double clicked, then without this fix, the views emit the
clicked() signal when the mousebutton is released after the double click
event. This is unexpected and wrong.

QAbstractItemView keeps track of the item the mouse was pressed on, to
verify that the release occurred on the same item before emitting
clicked, and to make sure we have a valid pressed item before initiating
drag'n'drop. By resetting d->pressedItem when a double click has been
handled, we can prevent the emission of a clicked signal in the next
release event.

[ChangeLog][QtWidgets][QTreeView] Don't emit clicked signal after a
doubleClicked signal.

Fixes: QTBUG-77771
Change-Id: I05988e9e2222157f4216cebc40c22507e8d83b82
Reviewed-by: André de la Rocha <andre.rocha@qt.io>
Reviewed-by: Jesus Fernandez <jsfdez@gmail.com>

src/widgets/itemviews/qabstractitemview.cpp

@@ -1966,6 +1966,7 @@ void QAbstractItemView::mouseDoubleClickEvent(QMouseEvent *event)
     if ((event->button() == Qt::LeftButton) && !edit(persistent, DoubleClicked, event)
         && !style()->styleHint(QStyle::SH_ItemView_ActivateItemOnSingleClick, 0, this))
         emit activated(persistent);
+    d->pressedIndex = QModelIndex();
 }
 
 #if QT_CONFIG(draganddrop)

src/widgets/itemviews/qtreeview.cpp

@@ -1943,6 +1943,7 @@ void QTreeView::mouseDoubleClickEvent(QMouseEvent *event)
         if (!style()->styleHint(QStyle::SH_ItemView_ActivateItemOnSingleClick, 0, this))
             emit activated(persistent);
 
+        d->pressedIndex = QModelIndex();
         d->executePostedLayout(); // we need to make sure viewItems is updated
         if (d->itemsExpandable
             && d->expandsOnDoubleClick