Fix an error in DiffusionBrowseTableView with SVN repsositories with no lint information

Summary: If the repository has no lint information, we don't set a 'lint' key, but try to access it unconditionally later on.

Test Plan: Looked at an SVN repository browse view, saw no errors.

Reviewers: vrana, btrahan, codeblock

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2281

Differential Revision: https://secure.phabricator.com/D4359