Fix block length calculation to return a Result type and handle errors appropriately

[ToufeeqP]

Pull Request type

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• Bugfix

Description

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Testing Performed

Checklist

• I have performed a self-review of my own code.
• The tests pass successfully with cargo test.
• The code was formatted with cargo fmt.
• The code compiles with no new warnings with cargo build --release and cargo build --release --features runtime-benchmarks.
• The code has no new warnings when using cargo clippy.
• If this change affects documented features or needs new documentation, I have created a PR with a documentation update.