Disallow `None` values in `compute_elo`

background_task.py

@@ -99,7 +99,7 @@ class Matchmaking:
             model1 = self.find_model(model1[0], model1[1])
             model2 = self.find_model(model2[0], model2[1])
             result = row["result"]
-            if model1 is not None or model2 is not None:
+            if model1 is not None and model2 is not None:
                 self.compute_elo(model1, model2, row["result"])
                 self.matches["model1"].append(model1.author + "/" + model1.name)
                 self.matches["model2"].append(model2.author + "/" + model2.name)