Fixing crash in cloning empty SkPicture object

BUG=https://code.google.com/p/chromium/issues/detail?id=172062
TEST=Pictures unit test, test_clone_empty
Review URL: https://codereview.appspot.com/7223048

git-svn-id: http://skia.googlecode.com/svn/trunk@7430 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed