Phabricator notifications now supports repos without any project

Summary:
Currently, when a Phabricator payload for a commit comes,
it were assumed there were always projects to fetch.

This takes care of the following exception:

Exception type: ErrorException
Exception message: Undefined property: stdClass::$PHID-CMIT-pq...
In app/Phabricator/PhabricatorStory.php:140

It also solves another small code issue triggering an error.

Test Plan:
Phabricator resends failed requests at periodic intervals.

After it has been fixed, Phabricator sends it again.

12:18:20 < Wearg> dereckson created Notifications center.
12:23:24 < Wearg> dereckson set the image for Notifications center to F15185: profile.

Reviewers: dereckson

Differential Revision: http://devcentral.nasqueron.org/D114