Fix handling of empty activeOn

[gaspergrom]

Changes proposed ✍️

What

🤖 Generated by Copilot at ec2fe5d

This pull request fixes some bugs and improves the code quality of the automation workers for Slack. It adds safety checks for the platforms array in newMemberBlocks.ts, ensures the member data is fetched in newMemberWorker.ts, and handles errors better in slackWorker.ts.
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🤖 Generated by Copilot at ec2fe5d

To welcome new members with slack
We fixed some bugs in our stack
We checked member id
And platforms we did
And wrapped request.post in a catch

Why

How

🤖 Generated by Copilot at ec2fe5d

• Fix bug where member data would not be fetched if member id was falsy (link)
• Add safety checks for platforms array before accessing, spreading, and mapping it in slack message blocks and buttons (link, link, link)
• Move slack message creation and sending inside try-catch block for better error handling and readability in slackWorker.ts (link)

Checklist ✅

• Label appropriately with Feature, Improvement, or Bug.
• Add screehshots to the PR description for relevant FE changes
• New backend functionality has been unit-tested.
• API documentation has been updated (if necessary) (see docs on API documentation).
• Quality standards are met.