If to register the org::freedesktop::Akonadi::AgentManager dbus-interface fails cause e.g. dbus is not running, assert as early as possible and provide some hint rather then to assert later in qdbuspendingreply.cpp:273 cause d==NULL (btw cookies for those who finds the bug in QDBusPendingReplyData::argumentAt - hint: d can be NULL)

svn path=/trunk/KDE/kdepimlibs/; revision=978990