fix: un-ref'd source map causing memory leak

[DonIsaac]

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• Documentation or TypeScript types (it's okay to leave the rest blank in this case)
• Code changes

How did you verify your code works?

[DonIsaac]

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• wip: leaked JSGlobalObject in worker threads #16578
• fix: un-ref'd source map causing memory leak #16577 👈 (View in Graphite)
• fix: free VirtualMachine's mimalloc arena in debug builds #16576
• main

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[robobun]

^{Updated 2:57 PM PT - Jan 22nd, 2025}

❌ @DonIsaac, your commit 62d29f5 has 5 failures in #10351:

• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 12 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 22.04 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 20.04 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 24.04 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - SIGILL on 🍎 14 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 20.04 x64-baseline
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 24.04 x64-baseline
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 22.04 x64-baseline
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 12 x64-baseline
• test/js/web/broadcastchannel/broadcast-channel.test.ts - SIGILL on 🍎 13 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - SIGTRAP on 🍎 14 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 3.20 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 12 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 24.04 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 20.04 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 22.04 x64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - SIGTRAP on 🍎 13 aarch64
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 3.20 x64-baseline
• test/js/web/broadcastchannel/broadcast-channel.test.ts - segmentation fault on 🐧 3.20 x64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 20.04 aarch64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 22.04 aarch64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 24.04 aarch64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 20.04 x64-baseline
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 24.04 x64-baseline
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 22.04 x64-baseline
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🍎 14 aarch64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 20.04 x64
• test/js/node/worker_threads/worker_threads.test.ts - segmentation fault on 🐧 24.04 x64
• test/js/third_party/body-parser/express-bun-build-compile.test.ts - integer overflow on 🪟 2019 x64
• test/js/third_party/body-parser/express-bun-build-compile.test.ts - integer overflow on 🪟 2019 x64-baseline
• test/js/web/workers/worker.test.ts - segmentation fault on 🪟 2019 x64
• test/js/web/workers/worker.test.ts - segmentation fault on 🪟 2019 x64-baseline
• test/js/web/workers/worker.test.ts - segmentation fault on 🐧 20.04 aarch64
• test/js/web/workers/worker.test.ts - segmentation fault on 🐧 22.04 aarch64
• test/js/web/workers/worker.test.ts - SIGTRAP on 🍎 13 aarch64
• test/js/node/worker_threads/worker_destruction.test.ts - segmentation fault at address 0x5a170620000 on 🪟 2019 x64
• test/js/node/worker_threads/worker_destruction.test.ts - segmentation fault at address 0x3ad2a5f0000 on 🪟 2019 x64-baseline

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🧪   try this PR locally:

bunx bun-pr 16577