fix: index_put converter to handle multi-shape slicing with None

[chohk88]

Description

Previously, index_put converter passed all test cases but failed in a corner case where slicing is done using a multi-dimensional tensor together with None (e.g., tensor[None, idx_tensor]). This PR updates the converter to properly handle that case.

Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project (You can use the linters)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas and hacks
• I have made corresponding changes to the documentation
• I have added tests to verify my fix or my feature
• New and existing unit tests pass locally with my changes
• I have added the relevant labels to my PR in so that relevant reviewers are notified

[zewenli98]

Can you rebase on the latest main branch? If all CI tests pass after the rebase, then LGTM

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