Minor, touch up Exception rendering

Summary: Cleans up spacing, hides footer if nothing present, uses common colors.

Test Plan:
Write some typical for a designer code.

{F309840}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11824