QDBusAbstractAdaptor: Assert that the parent is not null

QDBusAbstractAdaptor is expected to be used with a parent.
Add an assertion that will fail if a user is using this
class incorrectly. That's easier to debug than a null
pointer dereference in QDBusAdaptorConnector::polish().

Fixes: QTBUG-18525
Change-Id: I1934475fe277e0cc08435d79f1d453d6576f0b1c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/dbus/qdbusabstractadaptor.cpp

@@ -104,6 +104,9 @@ void QDBusAbstractAdaptorPrivate::saveIntrospectionXml(QDBusAbstractAdaptor *ada
 QDBusAbstractAdaptor::QDBusAbstractAdaptor(QObject* obj)
     : QObject(*new QDBusAbstractAdaptorPrivate, obj)
 {
+
+    Q_ASSERT_X(obj, Q_FUNC_INFO, "Expected non-null parent");
+
     QDBusAdaptorConnector *connector = qDBusCreateAdaptorConnector(obj);
 
     connector->waitingForPolish = true;