fix mask issue when setting to null and back

[GoodBoyDigital]

Description of change

Fixes a little regression bug when doing the following:

 thing.mask = mask;
 thing.mask = null;
 thing.mask = mask; // would throw as mask effect refference was not removed.

Pre-Merge Checklist

• Tests and/or benchmarks are included
• Lint process passed (npm run lint)
• Tests passed (npm run test)

[korbit-ai]

My review is in progress 📖 - I will have feedback for you in a few minutes!

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[korbit-ai]

I have reviewed your code and did not find any issues!

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