ignore the expection which is threw by saxParser.write

The expection is threw from https://github.com/isaacs/sax-js/blob/master/lib/sax.js#L913, but it had be handled at https://github.com/isaacs/sax-js/blob/master/lib/sax.js#L644 before, so I ignore the first one which throw the error ungracefully.

However, maybe this is a bug of sax, not the xml2js, we should not just ignore it. Wish you a better idea.