PromptGuardian crashes if GOOGLE_API_KEY env var is invalid

[vhosakot]

PromptGuardian crashes if GOOGLE_API_KEY env var is invalid like below:

GOOGLE_API_KEY=junk1234

PG logs:

ERROR:    Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/starlette/routing.py", line 734, in lifespan
    async with self.lifespan_context(app) as maybe_state:
  File "/usr/local/lib/python3.11/site-packages/starlette/routing.py", line 610, in __aenter__
    await self._router.startup()
  File "/usr/local/lib/python3.11/site-packages/starlette/routing.py", line 711, in startup
    await handler()
  File "/usr/local/lib/python3.11/site-packages/prompt_guardian/server.py", line 76, in startup_event
    if prompt_guardian_app.state.gemini_prompt_guard.chat is None:
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'GeminiPromptGuard' object has no attribute 'chat'
ERROR:    Application startup failed. Exiting.

It'd be nice if PG prints an error in logs, similar to the below error seen in PG logs when OPENAI_API_KEY env var is invalid like OPENAI_API_KEY= junk1234:

Error code: 401 - {'error': {'message': 'Incorrect API key provided: junk1234. You can find your API key at https://platform.openai.com/account/api-keys.', 'type': 'invalid_request_error', 'param': None, 'code': 'invalid_api_key'}}