1233 no crash by empty group "()" while optimizing to "only()"

  1234 

  1235   $ try --optimize '::1 and ()'

  1236   (and

  1237     (dagrangepre

  1238       ('symbol', '1'))

  1239     (group

  1240       None))

  1241   * optimized:

  1242   (and

  1243     None

  1244     (func

  1245       ('symbol', 'ancestors')

  1246       ('symbol', '1')))

  1247   hg: parse error: missing argument

  1248   [255]

  1249