[python] fix for `_failsafe_deserialize` when response.json() is not valid

[msyyc]

Context: https://teams.microsoft.com/l/message/19:meeting_Yzk1ZDlkNzAtZTAzZi00OTQzLWE1MDAtNTFiYTljODcwYzc4@thread.v2/1747689998942?context=%7B%22contextType%22%3A%22chat%22%7D

For https://github.com/Azure/azure-sdk-for-python/blob/0608404707249be5e2984ebac39d59dfbd24821d/sdk/ai/azure-ai-agents/azure/ai/agents/operations/_operations.py#L1458:

error = _failsafe_deserialize(_models.AgentV1Error, response.json())

if response.json() is not valid JSON, we will raise deserialization error instead of HttpResponseError which will confuse SDK users.

[msyyc]

If response.json() is not valid, json.decoder.JSONDecodeError will be raised (e.g. source code in azure-core).

So one solution is we add try-except like:

try:
    error = _failsafe_deserialize(_models.AgentV1Error, response.json())
except json.decoder.JSONDecodeError:
    error = None

[tadelesh]

we should pass response to _failsafe_deserialize. related pr: #5270.