Do not fail when scanning rootfs

[pombredanne]

When scanning this QCOW2 image https://cloud-images.ubuntu.com/minimal/releases/noble/release/ubuntu-24.04-minimal-cloudimg-amd64.img using the analyze_root_filesystem_or_vm_image pipline we get this error:

2024-12-09 09:06:09.384 Step [collect_and_create_system_packages] starting
2024-12-09 09:15:04.434 Pipeline failed

Task output

'>' not supported between instances of 'str' and 'NoneType'

Traceback:
  File "/opt/scancodeio/aboutcode/pipeline/__init__.py", line 199, in execute
    step(self)
  File "/opt/scancodeio/scanpipe/pipelines/root_filesystem.py", line 88, in collect_and_create_system_packages
    rootfs.scan_rootfs_for_system_packages(self.project, rfs)
  File "/opt/scancodeio/scanpipe/pipes/rootfs.py", line 283, in scan_rootfs_for_system_packages
    most_seen_namespace = max(namespace_counts)
                          ^^^^^^^^^^^^^^^^^^^^^

[tdruez]

Fixed in #1464