graph: allow 0 connections in new network

[pinheadmz]

closes #780

[pinheadmz]

cc @naiyoma

[naiyoma]

tested, this works, thanks

caddy:
  enabled: true
fork_observer:
  configQueryInterval: 10
  enabled: true
nodes:
- addnode: []
  image:
    tag: '29.0'
  name: tank-0000
- addnode: []
  image:
    tag: '29.0'
  name: tank-0001
- addnode: []
  image:
    tag: '29.0'
  name: tank-0002
- addnode: []
  image:
    tag: '29.0'
  name: tank-0003