patch can be None in the exception, causing a secondary exception.
patch can be None in the exception, causing a secondary exception.

R=csharp@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11232069

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@163646 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools