svndiff.py: properly handle empty expectations dictionary
BUG=skia:1588
R=jvanverth@google.com

Review URL: https://codereview.chromium.org/23769005

git-svn-id: http://skia.googlecode.com/svn/trunk@11078 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed