Fix batch index for cascade roi head (#2078)

Author: grimoire

mmdeploy/codebase/mmdet/models/roi_heads/cascade_roi_head.py

@@ -69,7 +69,7 @@ def cascade_roi_head__predict_bbox(self,
             new_rois = get_box_tensor(new_rois)
             rois = new_rois.reshape(-1, new_rois.shape[-1])
             # Add dummy batch index
-            rois = torch.cat([rois.new_zeros(rois.shape[0], 1), rois], dim=-1)
+            rois = torch.cat([batch_index.flatten(0, 1), rois], dim=-1)
     cls_scores = sum(ms_scores) / float(len(ms_scores))
     bbox_preds = bbox_pred.reshape(batch_size, num_proposals_per_img, -1)
     rois = rois.reshape(batch_size, num_proposals_per_img, -1)