fix: allow for nodes without any edges (e.g. new player)

cutt/analysis.py

@@ -116,6 +116,7 @@ def graph_json(
             status_code=status.HTTP_404_NOT_FOUND, detail="no entries found"
         )
     G = nx.DiGraph()
+    G.add_nodes_from([n["id"] for n in nodes])
     G.add_weighted_edges_from([(e["source"], e["target"], e["size"]) for e in edges])
     in_degrees = G.in_degree(weight="weight")
     nodes = [