Prevent crashes when callbacks are called before that the ABook object has been destroyed (cherry picked from commit 5b341050877b4052fb63bfeb73416d5ced9eefcc)
Prevent crashes when callbacks are called before that the ABook object has been destroyed
(cherry picked from commit 5b341050877b4052fb63bfeb73416d5ced9eefcc)

Relates to task QTMOBILITY-134

enthought/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,KDE/android-qt-mobility,tmcguire/qt-mobility,KDE/android-qt-mobility,kaltsi/qt-mobility,KDE/android-qt-mobility,qtproject/qt-mobility,enthought/qt-mobility,kaltsi/qt-mobility,tmcguire/qt-mobility,enthought/qt-mobility,tmcguire/qt-mobility,kaltsi/qt-mobility,enthought/qt-mobility,KDE/android-qt-mobility,kaltsi/qt-mobility,kaltsi/qt-mobility,qtproject/qt-mobility,tmcguire/qt-mobility,qtproject/qt-mobility