参数如下：

{"out_trade_no":"1145605634234867736","out_refund_no":"1145605727147089946_r","refund_account":"REFUND_SOURCE_UNSETTLED_FUNDS","total_fee":"3800","refund_fee":"3800","refund_fee_type":"CNY","sub_mch_id":"1509620871"}

异常如下: 

org.xml.sax.SAXParseException: Premature end of file.
	at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:257) ~[?:1.8.0_45]
	at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:348) ~[?:1.8.0_45]
	at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:121) ~[?:1.8.0_45]
	at com.github.wxpay.sdk.WXPayUtil.xmlToMap(WXPayUtil.java:43) ~[wxpay-sdk-0.0.6.jar:0.0.6]
	at com.github.wxpay.sdk.WXPay.processResponseXml(WXPay.java:193) ~[wxpay-sdk-0.0.6.jar:0.0.6]
	at com.github.wxpay.sdk.WXPay.refund(WXPay.java:506) ~[wxpay-sdk-0.0.6.jar:0.0.6]
	at com.github.wxpay.sdk.WXPay.refund(WXPay.java:483) ~[wxpay-sdk-0.0.6.jar:0.0.6]

请问：退款请求参数有问题吗？为什么会报错？