R1:1db281bcd1bb

Fix a possible `count(null)` in PHUIInfoView

Summary:
See <https://discourse.phabricator-community.org/t/php7-2-exception-count-parameter-must-be-an-array-or-an-object-that-implements-countable/1031>.

PHP7.2 raises a warning about `count(scalar)` (GREAT!) and we have one here if the caller doesn't `setErrors(...)`.

Test Plan: Sanity-checked usage of `$this->errors`.

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D18964