fix: readAllNotifications message not working

[anatawa12]

What

Fix #14367

readAllNotificationsメッセージにペイロードがないときに動かなくなっていたのを修正します

Why

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[github-actions]

このPRによるapi.jsonの差分

差分はこちら

Get diff files from Workflow Page

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 21 lines in your changes missing coverage. Please review.

Project coverage is 39.92%. Comparing base (61eec93) to head (d2544a0).
Report is 260 commits behind head on develop.

Files	Patch %	Lines
...ckages/backend/src/server/api/stream/Connection.ts	12.50%	14 Missing ⚠️
...end/src/server/api/stream/channels/reversi-game.ts	25.00%	3 Missing ⚠️
packages/backend/src/misc/json-value.ts	50.00%	2 Missing ⚠️
...kend/src/server/api/stream/channels/queue-stats.ts	50.00%	1 Missing ⚠️
...end/src/server/api/stream/channels/server-stats.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #14374       +/-   ##
============================================
- Coverage    66.21%   39.92%   -26.30%     
============================================
  Files          990     1544      +554     
  Lines       117137   190368    +73231     
  Branches      4489     2692     -1797     
============================================
- Hits         77568    75995     -1573     
- Misses       39538   113813    +74275     
- Partials        31      560      +529     

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[syuilo]

🙏
テスト追加できたりするかしら

[anatawa12]

NotificationService.readAllNotificationが呼ばれたことがどうやってテストしたらいいかがいい方法が思いつかないので難しいかもです

[syuilo]

🙏🏻