Fix getObjectType and getProjectsPHIDs exceptions

Summary:
Sometimes, a story is sent without any objectPHID field.
For example, test notifications to verify Aphlict settings have
no object attached.

This code handles those cases adding extra check for data presence.

Fixes T917.

Test Plan: Fire a failed notification

Reviewers: dereckson

Maniphest Tasks: T917

Differential Revision: https://devcentral.nasqueron.org/D489