Fix get all collections when no properties and named vector

[rlmanrique]

When running the function: collections.list_all() the following error happens when using a collection with named vector and no properties.

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/collections/collections/executor.py", line 392, in list_all
    return executor.execute(
           ~~~~~~~~~~~~~~~~^
        response_callback=resp,
        ^^^^^^^^^^^^^^^^^^^^^^^
    ...<2 lines>...
        error_msg="Get all collections",
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/connect/executor.py", line 99, in execute
    return cast(T, exception_callback(e))
                   ~~~~~~~~~~~~~~~~~~^^^
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/connect/executor.py", line 38, in raise_exception
    raise e
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/connect/executor.py", line 95, in execute
    resp_call = response_callback(call)
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/collections/collections/executor.py", line 389, in resp
    return _collection_configs_simple_from_json(data)
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/collections/classes/config_methods.py", line 438, in _collection_configs_simple_from_json
    schema["class"]: _collection_config_simple_from_json(schema) for schema in schema["classes"]
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/collections/classes/config_methods.py", line 329, in _collection_config_simple_from_json
    vector_config=__get_vector_config(schema, simple=True),
                  ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "/Users/rodrigo/workspace/github/weaviate-cli/.venv/lib/python3.13/site-packages/weaviate/collections/classes/config_methods.py", line 280, in __get_vector_config
    props = vec_config.pop("properties", None)
            ^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'pop'

However, when the collection has no named vector, it's fine.

This PR fixes that

[orca-security-eu]

Orca Security Scan Summary

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