Confusion matrix native image-space fix (#2046)

test.py

@@ -178,7 +178,7 @@ def test(data,
                 tbox = xywh2xyxy(labels[:, 1:5])
                 scale_coords(img[si].shape[1:], tbox, shapes[si][0], shapes[si][1])  # native-space labels
                 if plots:
-                    confusion_matrix.process_batch(pred, torch.cat((labels[:, 0:1], tbox), 1))
+                    confusion_matrix.process_batch(predn, torch.cat((labels[:, 0:1], tbox), 1))
 
                 # Per target class
                 for cls in torch.unique(tcls_tensor):