effects/overview: Call base QQuickItem::geometryChanged() in ExpoLayout

According to the Qt documentation, if an item overrides the
geometryChanged() method, it must call the base class method.

QQuickItem::geometryChanged() is responsible for emitting signals such
as xChanged(), yChanged(), etc.

src/effects/overview/expolayout.cpp

@@ -286,6 +286,7 @@ void ExpoLayout::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeo
     if (newGeometry.size() != oldGeometry.size()) {
         scheduleUpdate();
     }
+    QQuickItem::geometryChanged(newGeometry, oldGeometry);
 }
 
 static int distance(const QPoint &a, const QPoint &b)