chore: collapse duplicate logic

[ciband]

Summary

Reduced two if blocks to a single if block since their conditions
were exactly the same and they were sequencial statements.

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[ghost]

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[spkjp]

This breaks the entire signature deserialization. We need to perform this check after each read, since otherwise, whenever there is no second signature, it will attempt to read non-existing or wrong bytes.

[ghost]

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