private void returnCurrentSchema() {
        if (poolItem != null) {
            schemaPool.returnObject(poolItem, true);
            poolItem = null;
        }
    }
Sends characters to the current validator handler.

@param ch     Characters.
@param start  Start of char buffer.
@param length Number of chars to send.
@throws SAXException Not thrown.
@see stroom.pipeline.filter.AbstractXMLFilter#characters(char[],
int, int)
stroom-pipeline/src/main/java/stroom/pipeline/filter/SchemaFilter.java