if (value == null)
if (value == null || value.length == 0)
	public long add(byte[] value) throws ReadOnlyException {		if (value == null)			return -1;		// overflow value?		if (value.length > fileHeader.getWorkSize()) {			LOG.debug("creating overflow page");			OverflowDOMPage overflow = new OverflowDOMPage();			overflow.write(value);			byte[] pnum = ByteConversion.longToByte(overflow.getPageNum());			return add(pnum, true);		} else			return add(value, false);	}