Incorrect (?) rightmostFailurePos w/ Param

[pdubroy]

  const g = ohm.grammar(`
    G {
      Start = twice<"b">
      twice<x> = x x
    }`);
  const r = g.match('b c');
  t.is(r.getRightmostFailurePosition(), 2);

This fails. The reported (actual) failure position is 1, but I believe it should be 2 (after space skipping).

@alexwarth wdyt?