@Override
    public String onMapChangeBatchEnd(final long processedCount) {
        if (map == null || processedCount == 0) {
            return null;
        }
        return flushMapChanges();
    }
mimics {@link #removeItem(MarkerInterface)} but w/o calling 'populate'
main/src/main/java/cgeo/geocaching/unifiedmap/geoitemlayer/MapsforgeVtmGeoItemLayer.java