PyTorch Hub and autoShape update (#1415)

* PyTorch Hub and autoShape update

* comment x for imgs

* reduce comment

test.py

@@ -126,7 +126,7 @@ def test(data,
             tcls = labels[:, 0].tolist() if nl else []  # target class
             seen += 1
 
-            if pred is None:
+            if len(pred) == 0:
                 if nl:
                     stats.append((torch.zeros(0, niou, dtype=torch.bool), torch.Tensor(), torch.Tensor(), tcls))
                 continue