Fix loading tipsets past the range

[elmattic]

Summary of changes

Changes introduced in this pull request:

• Fix range tipset lookups that were not taking null rounds into account.

forest-tool api compare --lotus /ip4/127.0.0.1/tcp/1234/http --forest /ip4/127.0.0.1/tcp/2345/http forest_snapshot_calibnet_2025-01-30_height_2364216.forest.car.zst --filter EthGetLogs -n 900
| RPC Method                 | Forest | Lotus |
|----------------------------|--------|-------|
| Filecoin.EthGetLogs (1800) | Valid  | Valid |

Reference issue to close (if applicable)

Closes #5213

Other information and links

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation. All new code adheres to the team's documentation standards,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

[LesnyRumcajs]

rock-solid