error message unicorn

class org.apache.xmlbeans.XmlException
error: Illegal XML character: 0x0
org.apache.xmlbeans.impl.piccolo.io.IllegalCharException: Illegal XML
character: 0x0
	at org.apache.xmlbeans.impl.piccolo.xml.UTF8XMLDecoder.decode(UTF8XMLDecoder.java:196)
	at org.apache.xmlbeans.impl.piccolo.xml.XMLStreamReader$FastStreamDecoder.read(XMLStreamReader.java:762)
	at org.apache.xmlbeans.impl.piccolo.xml.XMLStreamReader.read(XMLStreamReader.java:162)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.yy_refill(PiccoloLexer.java:3474)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.yynextChar(PiccoloLexer.java:3721)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.parseElementNameNS(PiccoloLexer.java:2351)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.parseOpenTagNS(PiccoloLexer.java:1455)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.parseTagNS(PiccoloLexer.java:1362)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.parseXMLNS(PiccoloLexer.java:1293)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.parseXML(PiccoloLexer.java:1261)
	at org.apache.xmlbeans.impl.piccolo.xml.PiccoloLexer.yylex(PiccoloLexer.java:4808)
	at org.apache.xmlbeans.impl.piccolo.xml.Piccolo.yylex(Piccolo.java:1290)
	at org.apache.xmlbeans.impl.piccolo.xml.Piccolo.yyparse(Piccolo.java:1400)
	at org.apache.xmlbeans.impl.piccolo.xml.Piccolo.parse(Piccolo.java:714)
	at org.apache.xmlbeans.impl.store.Locale$SaxLoader.load(Locale.java:3454)
	at org.apache.xmlbeans.impl.store.Locale.parseToXmlObject(Locale.java:1276)
	at org.apache.xmlbeans.impl.store.Locale.parseToXmlObject(Locale.java:1263)
	at org.apache.xmlbeans.impl.schema.SchemaTypeLoaderBase.parse(SchemaTypeLoaderBase.java:345)
	at org.w3.x2009.x10.unicorn.observationresponse.ObservationresponseDocument$Factory.parse(Unknown
Source)
	at org.w3c.unicorn.response.impl.DefaultResponseXBeans.<init>(DefaultResponseXBeans.java:60)
	at sun.reflect.GeneratedConstructorAccessor47.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at org.w3c.unicorn.response.ResponseFactory.getResponse(ResponseFactory.java:24)
	at org.w3c.unicorn.request.URIRequest.doRequest(URIRequest.java:141)
	at org.w3c.unicorn.RequestThread.run(RequestThread.java:66)

org.apache.xmlbeans.impl.store.Locale$SaxLoader.load(Locale.java:3486)
org.apache.xmlbeans.impl.store.Locale.parseToXmlObject(Locale.java:1276)
org.apache.xmlbeans.impl.store.Locale.parseToXmlObject(Locale.java:1263)
org.apache.xmlbeans.impl.schema.SchemaTypeLoaderBase.parse(SchemaTypeLoaderBase.java:345)
org.w3.x2009.x10.unicorn.observationresponse.ObservationresponseDocument$Factory.parse(Unknown
Source)
org.w3c.unicorn.response.impl.DefaultResponseXBeans.<init>(DefaultResponseXBeans.java:60)
sun.reflect.GeneratedConstructorAccessor47.newInstance(Unknown Source)
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
java.lang.reflect.Constructor.newInstance(Constructor.java:513)
org.w3c.unicorn.response.ResponseFactory.getResponse(ResponseFactory.java:24)
org.w3c.unicorn.request.URIRequest.doRequest(URIRequest.java:141)
org.w3c.unicorn.RequestThread.run(RequestThread.java:66)