Issue:
When fetching statistics for nodes and a node has no lastHeard value or has a null lastHeard value it becomes a None type which is not handled correctly.
Solution:
Ignore all nodes with a None type lastSeen so they won't interfere with the calculation
Issue: When fetching statistics for nodes and a node has no lastHeard value or has a null lastHeard value it becomes a None type which is not handled correctly.
Solution: Ignore all nodes with a None type lastSeen so they won't interfere with the calculation