For a picture playback with nothing written, use an empty SkData.

This prevents crashing when attempting to access fOpData.

BUG=https://code.google.com/p/skia/issues/detail?id=870

Review URL: https://codereview.appspot.com/6499108

git-svn-id: http://skia.googlecode.com/svn/trunk@5550 2bbb7eff-a529-9590-31e7-b0007b416f81
3 files changed