refactor: don't set shape based on unitialised topology

This doesn't make any difference to the outcome - we were simply
setting the shape in the NodeSummary to "", which is what it starts
out as - but looks less weird in the code.

render/detailed/summary.go

@@ -134,14 +134,15 @@ func (n NodeSummary) SummarizeMetrics() NodeSummary {
 }
 
 func baseNodeSummary(r report.Report, n report.Node) NodeSummary {
-	t, _ := r.Topology(n.Topology)
 	summary := NodeSummary{
 		ID:        n.ID,
-		Shape:     t.GetShape(),
 		Linkable:  true,
 		Parents:   Parents(r, n),
 		Adjacency: n.Adjacency,
 	}
+	if t, ok := r.Topology(n.Topology); ok {
+		summary.Shape = t.GetShape()
+	}
 	if _, ok := n.Counters.Lookup(n.Topology); ok {
 		// This is a group of nodes, so no metadata, metrics, tables
 		return summary