fix "unroll for" failure (InvalidCPos) #3426

Job	Run time
EasyCrypt compilation (nix)	42s
Fetch EasyCrypt External Projects Matrix	2s
EasyCrypt compilation (opam)	1m 18s
Check EasyCrypt Libraries (unit)	1m 12s
Check EasyCrypt External Projects (jasmin-eclib, https://github.com/jasmin-lang/jasmin, main, ecl...	1m 52s
Check EasyCrypt Libraries (stdlib)	5m 1s
Check EasyCrypt External Projects (sha3, https://gitlab.com/easycrypt/sha3, next, ., config/tests...	12m 8s
Check EasyCrypt Libraries (examples)	3m 13s
Check EasyCrypt External Projects (cryptobox, https://gitlab.com/fdupress/ec-cryptobox, next, ., ...	2m 20s
Check EasyCrypt External Projects (xsalsa20, https://gitlab.com/fdupress/ec-xsalsa, master, ., co...	1m 42s
Check EasyCrypt External Projects (xmss-acai, https://github.com/MM45/FV-XMSS-EC, master, ., conf...	7m 44s
Check EasyCrypt External Projects (xmss-fsai, https://github.com/MM45/FV-XMSS-EC, master, ., conf...	6m 49s
Check EasyCrypt External Projects (sphincsplus, https://github.com/MM45/FV-SPHINCSPLUS-EC, master...	20m 58s
Check EasyCrypt External Projects (set-status)	1s
Notification	3s
	1h 5m 5s

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