Handling Empty Diagram

[lizliz]

There doesn't seem to be a catch to deal with empty diagrams. This example came up when someone in class was generating the simple persistence diagram data set from normal distributions, and it was throwing errors. My best guess is that because they were picking a mean that was right on the diagonal, sometimes they would get a diagram where all pulled points were dropped.

The long term solution for this is likely to have an actual diagram class that can handle things.....