Fix for `startAt fails when querying secondary indices`

[blazejkustra]

Summary:

Code sample:

Model

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General

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GitHub linked issue:

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Type of change:

• [ ] Bug fix
• [ ] Feature implementation
• [ ] Documentation improvement
• [ ] Testing improvement
• [ ] Something not listed here

Is this a breaking change?

• [ ] YES 🚨
• [ ] No

Other:

• [ ] I have searched through the GitHub pull requests to ensure this PR has not already been submitted
• [ ] I have updated the Dynamode documentation (if required)
• [ ] I have added/updated the Dynamode test cases (if required)
• [ ] I agree that all changes made in this pull request may be distributed and are made available in accordance with the Dynamode License.