ListView doesn't show new 1st item currentItem is removed.

ListView doesn't show new 1st item currentItem is removed.

If the new 1st item becomes the currentItem after removal
it was positioned incorrectly because the currentItem is positioned
based on visibleIndex, which was updated after the currentItem
was updated.  Move visibleIndex update before currentItem update.

Change-Id: Iaf92a41eefe7bce093e3000d17f5496dba144bcd
Fixes: QTBUG-20575
Reviewed-on: http://codereview.qt.nokia.com/2316
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bea Lam <bea.lam@nokia.com>