Item spacing can break about flexmasonry

[JoshuaCrewe]

@matthewdixon has just supplied me with a much more simple and elegant solution.
align-content: flex-start; on the container.

[JoshuaCrewe]

I realised that the link to the pen I provided was not the right version and wasn't showing the bug at all! I have updated the pen which now shows what I am experiencing.

The crux of the issue is if 3 columns are desired but only two items supplied the layout doesn't work. The workaround it to make sure there are more than two items which is most likely the case but when it is client uploaded can't always rely on this.