Description of problem:
System Settings -> Workspace Behaviour crashes with 

#6  0x00007f45ed2a8157 in QObject::setProperty(char const*, QVariant const&) () at /lib64/libQtCore.so.4
#7  0x00007f45c7670e52 in MainConfigurationWidget::MainConfigurationWidget(QWidget*, QList<QVariant>) (this=this@entry=0x25408b0, parent=parent@entry=0x2356c00, args=args@entry=...) at /usr/src/debug/kactivities-4.13.3/src/workspace/settings/MainConfigurationWidget.cpp:149
#8  0x00007f45c7672c50 in KPluginFactory::createInstance<MainConfigurationWidget, QWidget>(QWidget*, QObject*, QList<QVariant> const&) (parentWidget=<optimized out>, parent=<optimized out>, args=...) at /usr/include/kde4/kpluginfactory.h:477

Relevant portion of MainConfigurationWidget.cpp shows
146:    QDeclarativeComponent component(engine, QUrl(QString(KAMD_DATA_DIR) + "workspace/settings/BlacklistApplicationView.qml"));
147:    qDebug() << "Errors: " << component.errors();
148:    d->viewBlacklistedApplicationsRoot = qobject_cast<QGraphicsObject *>(component.create());
149:    d->viewBlacklistedApplicationsRoot->setProperty("width", d->viewBlacklistedApplications->width());

What's happening is that the qobject_cast on line 148 is null, because QString(KAMD_DATA_DIR) + "workspace/settings/BlacklistApplicationView.qml" (which is /usr/share/kde4/apps/activitymanager/workspace/settings/BlacklistApplicationView.qml) is missing. This last file is in the kactivities package, which however cannot be installed, since it is obsoleted by kf5-kactivities.

Version-Release number of selected component (if applicable):
kactivities-libs-4.13.3-6.fc22.x86_64

How reproducible:
Always

Steps to Reproduce:
1. Attempt to open System Settings -> Workspace Behaviour

Additional info:
Simplest fix is probably to have kactivities-libs own the file, resp. the whole of %{_kde4_appsdir}/activitymanager/.