WebComment: fix detection of restricted reviews
WebComment: fix detection of restricted reviews

* Fix detection of whether a review is restricted or public, making the
  failed web test case to work again.

* Note that the bug was due to `x and y or z' technique that is dangerous
  to use when y may be false, such as empty string.  It is safer instead
  to use `(x and [y] or [z])[0]' technique because `[y]' is always true
  regardless of the value of y.  However, the present fix commits the
  simple, more readable, and less error-prone if/else alternative.

tiborsimko/invenio,inveniosoftware/invenio,tiborsimko/invenio,inveniosoftware/invenio