On my big screen the photo is 2-3 times normal and the crack (if it is a crack) appears to be at the back edge propagating both ways from the corner. At a minimum I would do better than the naked eye and either look at it with a magnifying glass or a clear blown up photo image. Maybe clean a few of the burrs away first for a clearer picture.I might be a little anal as my background is in Aeronautical Engineering and cracks are the root of all evil.

If it does break, think of which part of you anatomy hits the top tube first and how important is that to you.