Updatelayers unexpectedly fails if layer is 'None'

[afabiani]

Even in the case the option ignore errors is set to True, this will fail due to a missing check on the layer object.

Traceback (most recent call last):
  File "/usr/src/minerva_cczis_geonode/manage.py", line 31, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.10/site-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.10/site-packages/django/core/management/__init__.py", line 413, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.10/site-packages/django/core/management/base.py", line 354, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.10/site-packages/django/core/management/base.py", line 398, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.10/site-packages/geonode/geoserver/management/commands/updatelayers.py", line 109, in handle
    output = gs_slurp(
  File "/usr/local/lib/python3.10/site-packages/geonode/geoserver/helpers.py", line 785, in gs_slurp
    layer.set_processing_state("FAILED")
AttributeError: 'NoneType' object has no attribute 'set_processing_state'