Fix bad variable causing aphlict to fail to start with no "logs" config

Summary: Fixes T10863. See that task for discussion.

Test Plan:

• Configured aphlict with no "logs".
• Started aphlict.
  • Before change: exception.
  • After change: worked.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10863

Differential Revision: https://secure.phabricator.com/D15788