Always return something.

Change-Id: I39a357295eae82b2af8b97c964924965c74e0fbd
Reviewed-on: http://codereview.qt-project.org/5623
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>

src/plugins/accessible/widgets/complexwidgets.cpp

@@ -1714,6 +1714,7 @@ QAccessibleInterface* QAccessibleComboBox::child(int index) const
     } else if (index == 1 && comboBox()->isEditable()) {
         return QAccessible::queryAccessibleInterface(comboBox()->lineEdit());
     }
+    return 0;
 }
 
 /*! \reimp */