plainLiteral get "Empty lang tag"

[comedinha]

https://github.com/SmartDataAnalytics/jena-sparql-api/commit/064310652219112f8c6d4b7e41e654bbdb73630b#diff-b5e914297109c27ea74cc323383d632c

this change affect function plainLiteral and if you not put lang the sparqlify-csv not work.

https://github.com/SmartDataAnalytics/Sparqlify/blob/master/sparqlify-examples/src/main/resources/sparqlify-examples/csv/example1.sml

To work need:

Prefix ex: <http://example.org/>
Prefix xsd: <http://www.w3.org/2001/XMLSchema#>
Create View Template test As
  Construct {
    ?s
      ex:name ?n ;
      ex:age ?a ;
      ex:gender ?g ;
      ex:email ?e ;
      ex:isPositive "true"^^xsd:boolean .
  }
  With
    ?s = uri(ex:, ?name)
    ?n = plainLiteral(?name, "en")
    ?a = plainLiteral(?age, "en")
    ?g = plainLiteral(?gender, "en")
    ?e = plainLiteral(?email, "en")

/*
Prefix ex: <http://example.org/>
Create View Template test As
  Construct {
    ?s ex:label ?o
  }
  With
    ?s = uri(ex:, ?1)
    ?o = plainLiteral(?2, "en")
*/