SAP_XI_IDOC/IDOCFlatToXmlConvertor gives error java.lang.StringIndexOutOfBoundsException: String index out of range: -1

In my Sender CC, I am using SAP_XI_IDOC/IDOCFlatToXmlConvertor module

I am getting the following error

MP: processing local module localejbs/SAP_XI_IDOC/IDOCFlatToXmlConvertor

Error : java.lang.StringIndexOutOfBoundsException: String index out of range: -1

Any help is highly appreciated !!!