Unexpected runtime error

The runtime has encountered an unexpected error.

Error source

Page Name:/allegato.xsp
Control Id: _id247

Exception

com.ibm.xsp.exception.EvaluationExceptionEx: Error while executing JavaScript computed expression
Error while executing JavaScript computed expression
Script interpreter error, line=5, col=19: [TypeError] Exception occurred calling method NotesDatabase.getDocumentByUNID(java.lang.String) Invalid universal id
Invalid universal id

JavaScript code

   1: var db:NotesDatabase = getCurrentDatabase()
   2: if(param.source)
   3: 	return db.getDocumentByUNID(param.source)
   4: else if(param.documentId)
   5: 	return db.getDocumentByUNID(param.documentId)
   6: else
   7: 	return null;

Stack Trace