fix: Enhance null handling for input and output token details in Usage class#2192

seratch merged 2 commits intoopenai:mainopenai/openai-agents-python:mainfrom

aliasgher-sketric:sketric/fix-usage-null-handlingaliasgher-sketric/openai-agents-python:sketric/fix-usage-null-handlingCopy head branch name to clipboard