Notify QQJSE::DW of expression deletion during dtor
Notify QQJSE::DW of expression deletion during dtor

QQmlJavaScriptExpression::DeleteWatcher's wasDeleted() function simply
checks to see if the pointer to the expression being watched is null.
This commit ensures that the DeleteWatcher's expression pointer is
set to null during QQJSE::dtor().

Change-Id: I566737bf30b4466ba96d771d9846fc3dd860cd2f
Reviewed-by: Michael Brasser <acf66a4a6ae67569abc58c29c7a264afd3e1cc1c@nokia.com>

matthewvogt/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,jfaust/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,crobertd/qtdeclarative,jfaust/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,crobertd/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,matthewvogt/qtdeclarative,jfaust/qtdeclarative,jfaust/qtdeclarative,matthewvogt/qtdeclarative,corngood/qtdeclarative,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,matthewvogt/qtdeclarative,crobertd/qtdeclarative,matthewvogt/qtdeclarative,matthewvogt/qtdeclarative,jfaust/qtdeclarative,corngood/qtdeclarative,corngood/qtdeclarative,crobertd/qtdeclarative,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,qmlc/qtdeclarative,qmlc/qtdeclarative,qmlc/qtdeclarative,corngood/qtdeclarative