fix: Use strict undefined check for taskId in completion event handlers#157

YunchuWang merged 2 commits intomainmicrosoft/durabletask-js:mainfrom

copilot-finds/bug/fix-truthy-check-on-task-idmicrosoft/durabletask-js:copilot-finds/bug/fix-truthy-check-on-task-idCopy head branch name to clipboard