R1:a1aedff90a86

Use PhutilInvalidStateException

Summary: Use `PhutilInvalidStateException` in `PonderVoteEditor`.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13269