fix(avm)!: to_radix_mem underfow

[IlyasRidhuan]

The write address underflows if dst_addr = 0 and num_limbs = 0

[IlyasRidhuan]

• #18715
• #18503 👈 (View in Graphite)
• merge-train/avm

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[IlyasRidhuan]

Does the pure version need any change?

ahh good catch!