Fix resize failure caused by zero-sized masks in PP-DocLayoutV3

[zhang-prog]

Description

This PR fixes a boundary issue in the _extract_polygon_points_by_masks method of PP-DocLayoutV3.

When running inference with a low confidence threshold, or due to coordinate clipping during scaling, the extracted cropped_mask can sometimes have a size of 0 (empty array). This leads to a failure in subsequent operations (such as resize or polygon extraction).

Changes

Added a defensive check in _extract_polygon_points_by_masks to handle empty masks before processing:

cropped_mask = masks[i, y_start:y_end, x_start:x_end]
# New check: Handle cases where the mask is empty or contains no positive values
if cropped_mask.size == 0 or np.sum(cropped_mask) == 0:
    polygon_points.append(rect)
    continue

[github-actions]

[For maintainers] Suggested jobs to run (before merge)

run-slow: pp_doclayout_v3

[zhang-prog]

@vasqu @zucchini-nlp @molbap PTAL. Thanks!