@Override
    public void endProcessing() {
        try {
            super.endProcessing();
        } finally {
            // Make sure there is no further allocation of the buffer.
            handler = null;
        }
    }
Called just after a pipeline has finished processing.

@see stroom.pipeline.filter.XMLFilter#endProcessing()
stroom-pipeline/src/main/java/stroom/pipeline/filter/BufferFilter.java