Fix performance issue

When the root node was collapsed, it also was selected due to the click event.
The sidebar was updated every time a new message was receivend,
effectivly inhibiting the "render the tree if you got nothing else to do" optimization to render anything at all.

Fixes #7

app/src/components/Sidebar/NodeStats.tsx

@@ -1,5 +1,6 @@
 import * as React from 'react'
 import * as q from '../../../../backend/src/Model'
+
 import { Typography } from '@material-ui/core'
 
 interface Props {