Fix utils.py nonzero() warning (#551)

utils/utils.py

@@ -599,7 +599,7 @@ def non_max_suppression(prediction, conf_thres=0.1, iou_thres=0.6, merge=False,
 
         # Detections matrix nx6 (xyxy, conf, cls)
         if multi_label:
-            i, j = (x[:, 5:] > conf_thres).nonzero().t()
+            i, j = (x[:, 5:] > conf_thres).nonzero(as_tuple=False).t()
             x = torch.cat((box[i], x[i, j + 5, None], j[:, None].float()), 1)
         else:  # best class only
             conf, j = x[:, 5:].max(1, keepdim=True)