Add more error handling in pod_manager consume_logs

[o-nikolas]

Despite a None check already existing here

We still regularly see the below traceback failing our system tests, particularly on the Lambda executor. This PR adds an additional try/catch for TypeError around this code to ensure we default to None in cases where the since_time is either None or some other unacceptable value.

Traceback (most recent call last):
  File "/opt/airflow/providers/cncf/kubernetes/src/airflow/providers/cncf/kubernetes/operators/pod.py", line 704, in execute_sync
  File "/var/lang/lib/python3.12/site-packages/tenacity/__init__.py", line 338, in wrapped_f
  File "/var/lang/lib/python3.12/site-packages/tenacity/__init__.py", line 477, in __call__
  File "/var/lang/lib/python3.12/site-packages/tenacity/__init__.py", line 378, in iter
  File "/var/lang/lib/python3.12/site-packages/tenacity/__init__.py", line 400, in <lambda>
  File "/var/lang/lib/python3.12/concurrent/futures/_base.py", line 449, in result
  File "/var/lang/lib/python3.12/concurrent/futures/_base.py", line 401, in __get_result
  File "/var/lang/lib/python3.12/site-packages/tenacity/__init__.py", line 480, in __call__
  File "/opt/airflow/providers/cncf/kubernetes/src/airflow/providers/cncf/kubernetes/operators/pod.py", line 777, in await_pod_completion
  File "/opt/airflow/providers/cncf/kubernetes/src/airflow/providers/cncf/kubernetes/utils/pod_manager.py", line 721, in fetch_requested_container_logs
  File "/opt/airflow/providers/cncf/kubernetes/src/airflow/providers/cncf/kubernetes/utils/pod_manager.py", line 604, in fetch_container_logs
  File "/opt/airflow/providers/cncf/kubernetes/src/airflow/providers/cncf/kubernetes/utils/pod_manager.py", line 529, in consume_logs
  File "/var/lang/lib/python3.12/site-packages/pendulum/datetime.py", line 1215, in __sub__
  File "/var/lang/lib/python3.12/site-packages/pendulum/datetime.py", line 712, in diff
  File "/var/lang/lib/python3.12/site-packages/pendulum/interval.py", line 183, in __init__
TypeError: 'NoneType' object cannot be converted to 'PyString'

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[o-nikolas]

CC @isaiahiruoha

[isaiahiruoha]

I thought this day would never come, changes lgtm 😁