Fix focusScopeItemChange setting crash

Delay focusScopeItemChange to after reparenting, to prevent
an invalid focusScopeItem pointer crash.

Task-number: QTBUG-21640
Reviewed-by: Martin Jones

Author: Damian Jansen

src/gui/graphicsview/qgraphicsitem.cpp

@@ -1157,7 +1157,6 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent, const Q
             if (q_ptr == fsi || q_ptr->isAncestorOf(fsi)) {
                 parentFocusScopeItem = fsi;
                 p->d_ptr->focusScopeItem = 0;
-                fsi->d_ptr->focusScopeItemChange(false);
             }
             break;
         }
@@ -1259,6 +1258,10 @@ void QGraphicsItemPrivate::setParentItemHelper(QGraphicsItem *newParent, const Q
     if (!inDestructor && (transformData || (newParent && newParent->d_ptr->transformData)))
         transformChanged();
 
+    // Reparenting is finished, now safe to notify the previous focusScopeItem about changes
+    if (parentFocusScopeItem)
+      parentFocusScopeItem->d_ptr->focusScopeItemChange(false);
+
     // Restore the sub focus chain.
     if (subFocusItem) {
         subFocusItem->d_ptr->setSubFocus(newParent);