fix: pgx closed batch return pointer if need #1959 (#1960)

Author: flymedllva

internal/codegen/golang/templates/pgx/batchCode.tmpl

@@ -107,7 +107,7 @@ func (b *{{.MethodName}}BatchResults) QueryRow(f func(int, {{.Ret.DefineType}},
      var {{.Ret.Name}} {{.Ret.Type}}
      if b.closed {
         if f != nil {
-          f(t, {{.Ret.Name}}, errors.New("batch already closed"))
+          f(t, {{if .Ret.IsPointer}}nil{{else}}{{.Ret.Name}}{{end}}, errors.New("batch already closed"))
         }
         continue
      }