Fix group animations crash for collapsing applets

#6  0x00007f4144b7d104 in QAbstractAnimation::group() const () from /opt/qt-git/lib/libQtCore.so.4
#7  0x00007f4144b846d0 in QAnimationGroup::insertAnimation(int, QAbstractAnimation*) () from /opt/qt-git/lib/libQtCore.so.4
#8  0x00007f41465ca9c5 in Context::ContextView::slotCollapseAnimationsFinished (this=0x354cd80) at /home/rick/amarok/src/context/ContextView.cpp:266

CCBUG: 282875