Fix typo and add test for invalid vaults. (backport #2535)

[mergify]

Changelist

Had a typo when returning valid/invalid vaults. Updated a test to catch this.

Test Plan

Unit test.

Author/Reviewer Checklist

• If this PR has changes that result in a different app state given the same prior state and transaction list, manually add the state-breaking label.
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• If this PR isn't state-breaking but has changes that modify behavior in PrepareProposal or ProcessProposal, manually add the label proposal-breaking.
• If this PR is one of many that implement a specific feature, manually label them all feature:[feature-name].
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• Manually add any of the following labels: refactor, chore, bug.

Summary by CodeRabbit

• New Features

  • Enhanced API functionality to handle multiple vault subaccounts, including validation for invalid entries.

• Bug Fixes

  • Improved data integrity by filtering vault mappings to include only those corresponding to valid perpetual markets.

• Tests

  • Added a new test case for scenarios involving two vault subaccounts, one being invalid, to ensure correct API behavior.

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This is an automatic backport of pull request #2535 done by [Mergify](https://mergify.com).