Make bot macro handler more graceful in the face of failure

Summary: Fixes T5883. The first time we hit an error we'll continue forward; we only bail after the second time. Instead, check for an error immediately

Test Plan: HA HA HA DID NOT TEST HA HA HA HA

Reviewers: btrahan, cburroughs

Reviewed By: cburroughs

Subscribers: epriestley

Maniphest Tasks: T5883

Differential Revision: https://secure.phabricator.com/D10265