Summary: See PHI1745. This callsite for "ChangesetParser" was not properly updated for recent changes.

Test Plan:
  - Set `metamta.differential.inline-patches` to 100.
  - Created a new revision with a small (<100 line) diff, with at least one reviewer.
  - Ran `bin/phd debug` and observed outbound mail queue with `bin/mail list-outbound`.
  - Before: fatal when trying to generate the inline changes for mail.
  - After: clean mail generation.

Differential Revision: https://secure.phabricator.com/D21270