fix: fix symbolic idxs interpolation for RODESolution

[AayushSabharwal]

Close #580

Checklist

• [ ] Appropriate tests were added
• [ ] Any code changes were done in a way that does not break public API
• [ ] All documentation related to code changes were updated
• [ ] The new code follows the contributor guidelines, in particular the SciML Style Guide and COLPRAC.
• [ ] Any new documentation only uses public API

Additional context

Add any other context about the problem here.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 40.84%. Comparing base (1624ee4) to head (d3c0827).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #673 +/- ## ========================================== + Coverage 40.80% 40.84% +0.04% ========================================== Files 55 55 Lines 4490 4490 ========================================== + Hits 1832 1834 +2 + Misses 2658 2656 -2 ```

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