R1:49f75d255492

Don't store empty copy:lines

Summary: The [[ https://secure.phabricator.com/diffusion/P/browse/master/src/applications/differential/parser/DifferentialChangesetParser.php;8d0918885da2c22b$1364 | callsite ]] is fine with that.

Test Plan: This diff.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3537