fail on empty keyword

[pvgenuchten]

  File "/usr/local/lib/python3.12/dist-packages/jinja2/environment.py", line 1304, in render
    self.environment.handle_exception()
  File "/usr/local/lib/python3.12/dist-packages/jinja2/environment.py", line 939, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "/usr/local/lib/python3.12/dist-packages/geodatacrawler/schemas/iso19139/main.j2", line 153, in top-level template code
    {% set keywords = get_charstring(value.get('keywords'), record.get('metadata',{}).get('language'), record.get('metadata',{}).get('language_alternate')) %}
    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/dist-packages/jinja2/utils.py", line 83, in from_obj
    if hasattr(obj, "jinja_pass_arg"):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
jinja2.exceptions.UndefinedError: 'None' has no attribute 'get'