source-mixpanel raises PyAirbyteNameNormalizationError

Opening a ticket per request from @aaronsteers in this [community slack thread](https://airbytehq.slack.com/archives/C06FZ238P8W/p1751321461271109)

I'm running into a PyAirbyteNameNormalizationError when I attempt to run the simple example below.

Example config.json
```json
{
"credentials": {
"project_id": 123,
"secret": "my_secret",
"username": "my_service_account"
},
"start_date": "2025-06-30T21:00:00Z",
"region": "US" #aside: this appears to be required, despite what https://docs.airbyte.com/integrations/sources/mixpanel suggests
}
```

Run this simple example:
```python

import airbyte as ab
from utils import load_json_config

mp_config = load_json_config("starbyte/sources/mixpanel/mixpanel_config.json")
mixpanel_source = ab.get_source(
name="source-mixpanel", config=mp_config, streams=["export"]
)
res = mixpanel_source.read(cache=ab.get_default_cache())

for name, records in res.streams.items():
print(f"Stream {name}: {len(records)} records")
```

Output
```
#From STDOUT
Started reading from source at 15:07:31:

• Read 68,074 records over 6.1 seconds (11,097.3 records/s, 8.33 MB/s).
• Received records for 1 streams:
• 68,074 export
```

```
#FROM LOG
tail -f /tmp/airbyte/logs/source-mixpanel/source-mixpanel-log-JZ1E2HRF0.log
2025-06-30 15:07:32 - INFO - Starting syncing SourceMixpanel
2025-06-30 15:07:32 - INFO - Marking stream export as STARTED
2025-06-30 15:07:32 - INFO - Setting state of SourceMixpanel stream to {}
2025-06-30 15:07:32 - INFO - Syncing stream: export
2025-06-30 15:07:43 - INFO - Marking stream export as RUNNING
```

This raises the following: See the full trace after this block.
```
Exception has occurred: PyAirbyteNameNormalizationError
Name cannot be empty after normalization. (PyAirbyteNameNormalizationError)
------------------------------------------------------------
PyAirbyteNameNormalizationError: Name cannot be empty after normalization.
Raw Name: ''
Normalization Result: ''
KeyError: ''

During handling of the above exception, another exception occurred:

File ".../simple_example.py", line 8, in
res = mixpanel_source.read(cache=ab.get_default_cache())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
airbyte.exceptions.PyAirbyteNameNormalizationError: Name cannot be empty after normalization. (PyAirbyteNameNormalizationError)
------------------------------------------------------------
PyAirbyteNameNormalizationError: Name cannot be empty after normalization.
Raw Name: ''
Normalization Result: '

```

---

```
Traceback (most recent call last):
File ".../.venv/lib/python3.11/site-packages/airbyte/records.py", line 161, in to_index_case
return self.quick_lookup[key]
~~~~~~~~~~~~~~~~~^^^^^
KeyError: ''

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File ".../.local/share/uv/python/cpython-3.11.11-macos-aarch64-none/lib/python3.11/runpy.py", line 198, in _run_module_as_main
return _run_code(code, main_globals, None,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".../.local/share/uv/python/cpython-3.11.11-macos-aarch64-none/lib/python3.11/runpy.py", line 88, in _run_code
exec(code, run_globals)
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/__main__.py", line 71, in
cli.main()
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 501, in main
run()
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/adapter/../../debugpy/launcher/../../debugpy/../debugpy/server/cli.py", line 351, in run_file
runpy.run_path(target, run_name="__main__")
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 310, in run_path
return _run_module_code(code, init_globals, run_name, pkg_name=pkg_name, script_name=fname)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 127, in _run_module_code
_run_code(code, mod_globals, init_globals, mod_name, mod_spec, pkg_name, script_name)
File ".../.vscode/extensions/ms-python.debugpy-2025.11.2025063001-darwin-arm64/bundled/libs/debugpy/_vendored/pydevd/_pydevd_bundle/pydevd_runpy.py", line 118, in _run_code
exec(code, run_globals)
File ".../simple_example.py", line 8, in
res = mixpanel_source.read(cache=ab.get_default_cache())
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".../.venv/lib/python3.11/site-packages/airbyte/sources/base.py", line 762, in read
result = self._read_to_cache(
^^^^^^^^^^^^^^^^^^^^
File ".../.venv/lib/python3.11/site-packages/airbyte/sources/base.py", line 846, in _read_to_cache
cache._write_airbyte_message_stream( # noqa: SLF001 # Non-public API
File ".../.venv/lib/python3.11/site-packages/airbyte/caches/base.py", line 362, in _write_airbyte_message_stream
cache_processor.process_airbyte_messages(
File ".../.venv/lib/python3.11/site-packages/airbyte/shared/sql_processor.py", line 282, in process_airbyte_messages
self.process_record_message(
File ".../.venv/lib/python3.11/site-packages/airbyte/shared/sql_processor.py", line 436, in process_record_message
self.file_writer.process_record_message(
File ".../.venv/lib/python3.11/site-packages/airbyte/_writers/file_writers.py", line 194, in process_record_message
record_dict=StreamRecord.from_record_message(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".../.venv/lib/python3.11/site-packages/airbyte/records.py", line 250, in from_record_message
return cls(
^^^^
File ".../.venv/lib/python3.11/site-packages/airbyte/records.py", line 223, in __init__
{
File ".../.venv/lib/python3.11/site-packages/airbyte/records.py", line 226, in
if self._stream_handler.to_index_case(k) in self._stream_handler.index_keys
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File ".../.venv/lib/python3.11/site-packages/airbyte/records.py", line 164, in to_index_case
self._normalizer.normalize(key)
File ".../.venv/lib/python3.11/site-packages/airbyte/_util/name_normalizers.py", line 81, in normalize
raise exc.PyAirbyteNameNormalizationError(
airbyte.exceptions.PyAirbyteNameNormalizationError: Name cannot be empty after normalization. (PyAirbyteNameNormalizationError)
------------------------------------------------------------
PyAirbyteNameNormalizationError: Name cannot be empty after normalization.
Raw Name: ''
Normalization Result: ''
```