Fix an issue where intracontent empty lines were incorrectly trimmed in quoted blocks
Summary: Fixes T13335. When processing quoted blocks, we remove leading empty lines. This logic incorrectly continued after encountering a nonempty line.
Test Plan: Added a test, made it pass. Previewed blocks in web UI.
Maniphest Tasks: T13335
Differential Revision: https://secure.phabricator.com/D20965