Keeping stats view open for a while produces index out of range error

[sardaukar]

Describe the bug
Keeping the stats window open for a given container for long periods of time eventually crashes with panic: runtime error: index out of range.

To Reproduce
Steps to reproduce the behavior:

1. selecting a running container
2. select stats view
3. wait for a while (I've seen it happen in a couple of hours)
4. see error

Expected behaviour
Stats view to not crash ever

Screenshots

Desktop (please complete the following information):

• OS: Debian Linux 9.9
• Lazydocker commit=50a6eb64ece25bc85c95c7223f6100bdbae6c69c, build date=2019-06-30T11:09:18Z, build source=binaryRelease, version=0.2.4, os=linux, arch=amd64

[sardaukar]

Still happens in commit=572ff63e858150d9cbec6f1ed67ff6d04258c9c0, build date=2019-07-03T14:21:59Z, build source=binaryRelease, version=0.4, os=linux, arch=amd64

[mjarkk]

@sardaukar @stdedos This will probably be fixed in the next release.