Cloud mode missing in O3 products

[Johaney-s]

Describe the bug
This line of code requires cloud_mode property in the S5p metadata of O3 products:

product_metadata.py, line 556:
"o3:cloud_mode": str(self._root.cloud_mode),

but the cloud_mode is missing in some O3 data.

To reproduce
I get this error for example on product 5b2ec3d2-cfa5-4c2d-8b25-b1894d1ffdb5: S5P_NRTI_L2__O3__PR_20240726T024524_20240726T025024_35152_03_020600_20240726T042829.nc
Expected behavior
I guess skipping it if missing and not throwing an exception would be suitable.

Traceback

Traceback (most recent call last):
  File "/home/johaney/Projects/DhusPytools/register_stac.py", line 436, in main
    item = stactools.sentinel5p.stac.create_item(os.path.join(metadata_dir, title))
  File "/home/johaney/Projects/DhusPytools/.venv/lib/python3.10/site-packages/stactools/sentinel5p/stac.py", line 87, in create_item
    item.properties.update({**product_metadata.metadata_dict})
  File "/home/johaney/Projects/DhusPytools/.venv/lib/python3.10/site-packages/stactools/sentinel5p/product_metadata.py", line 556, in metadata_dict
    "o3:cloud_mode": str(self._root.cloud_mode),
  File "src/netCDF4/_netCDF4.pyx", line 3131, in netCDF4._netCDF4.Dataset.__getattr__
  File "src/netCDF4/_netCDF4.pyx", line 3076, in netCDF4._netCDF4.Dataset.getncattr
  File "src/netCDF4/_netCDF4.pyx", line 1617, in netCDF4._netCDF4._get_att
  File "src/netCDF4/_netCDF4.pyx", line 2113, in netCDF4._netCDF4._ensure_nc_success
AttributeError: NetCDF: Attribute not found