[BUG] imx500_object_detection_demo.py with nanodet: fails with ValueError

[alexandre-perrin]

Describe the bug

Running imx500_object_detection_demo.py on Raspberry Pi 5 with IMX500 camera with --postprocess nanodet fails with: ValueError: operands could not be broadcast together with shapes (1,0,4) (1,3598,1)

To Reproduce

On Raspberry Pi 5 with AI Camera:
execute the demo script with --postprocess nanodet option:

python imx500_object_detection_demo.py --postprocess nanodet

Expected behaviour

Camera starts and application keeps running without crash.

Console Output, Screenshots

Traceback (most recent call last):
  File "/home/alexandre/aitrios-sdk-edge-app-dev/sample_apps/detection/python/imx500_object_detection_demo.py", line 246, in <module>
    last_results = parse_detections(picam2.capture_metadata())
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/alexandre/aitrios-sdk-edge-app-dev/sample_apps/detection/python/imx500_object_detection_demo.py", line 40, in parse_detections
    boxes, scores, classes = postprocess_nanodet_detection(
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/picamera2/devices/imx500/postprocess_nanodet.py", line 38, in postprocess_nanodet_detection
    distances = x * anchors[..., 2, None]
                ~~^~~~~~~~~~~~~~~~~~~~~~~
ValueError: operands could not be broadcast together with shapes (1,0,4) (1,3598,1)

Hardware :

Raspberry Pi 5 with AI Camera IMX500

Additional context