Hang after reporting a negative mean

[charig]

Unfortunately one of my benchmark was failling and my harness was reporting a negative mean (-1.0) to codespeed. When entering the changes tab after that the app halts or start lagging and becomes unusable. I know this is some unexpected behavior but it took me a while to realize was what really happening. So, the information may be valuable for others. Also, it would be good to have some error handling on that side.