pdf not getting generated for invoice with special char product name

[bharatkasodariya]

getting below error while downloading invoice with special char product name 'groß'

ERROR:  'The entity "szlig" was referenced, but not declared.'
16-Sep 12:48:57 WARN  (?:createPDFFromHTML:?) Can't load the XML resource (using TRaX transformer). org.xml.sax.SAXParseException: The entity "szlig" was referenced, but not declared. : javax.xml.transform.TransformerException: org.xml.sax.SAXParseException: The entity "szlig" was referenced, but not declared.
16-Sep 12:48:57 WARN  (?:getPdf:?) Problem creating PDF file : Can't load the XML resource (using TRaX transformer). org.xml.sax.SAXParseException: The entity "szlig" was referenced, but not declared.
org.xhtmlrenderer.util.XRRuntimeException: Can't load the XML resource (using TRaX transformer). org.xml.sax.SAXParseException: The entity "szlig" was referenced, but not declared.
   at org.xhtmlrenderer.resource.XMLResource$XMLResourceBuilder.createXMLResource(XMLResource.java:191)