@Override
    public void ignorableWhitespace(final char[] ch, final int start, final int length) throws SAXException {
        handler.ignorableWhitespace(ch, start, length);
    }
Receive notification of ignorable whitespace in element content.
<p>
<p>
Validating Parsers must use this method to report each chunk of
whitespace in element content (see the W3C XML 1.0 recommendation,
section 2.10): non-validating parsers may also use this method if they
are capable of parsing and using content models.
</p>
<p>
<p>
SAX parsers may return all contiguous whitespace in a single chunk, or
they may split it into several chunks; however, all of the characters in
any single event must come from the same external entity, so that the
Locator provides useful information.
</p>
<p>
<p>
The application must not attempt to read from the array outside of the
specified range.
</p>

@param ch     the characters from the XML document
@param start  the start position in the array
@param length the number of characters to read from the array
@throws org.xml.sax.SAXException any SAX exception, possibly wrapping another exception
@see #characters
stroom-pipeline/src/main/java/stroom/pipeline/filter/ContentHandlerAdaptor.java