fix "unroll for" failure (InvalidCPos) #3424

Job	Run time
EasyCrypt compilation (opam)	1m 17s
Fetch EasyCrypt External Projects Matrix	2s
EasyCrypt compilation (nix)	1m 26s
Check EasyCrypt Libraries (unit)	1m 15s
Check EasyCrypt External Projects (jasmin-eclib, https://github.com/jasmin-lang/jasmin, main, ecl...	2m 1s
Check EasyCrypt Libraries (stdlib)	5m 5s
Check EasyCrypt External Projects (sha3, https://gitlab.com/easycrypt/sha3, next, ., config/tests...	12m 19s
Check EasyCrypt Libraries (examples)	3m 6s
Check EasyCrypt External Projects (cryptobox, https://gitlab.com/fdupress/ec-cryptobox, next, ., ...	2m 16s
Check EasyCrypt External Projects (xsalsa20, https://gitlab.com/fdupress/ec-xsalsa, master, ., co...	1m 44s
Check EasyCrypt External Projects (xmss-acai, https://github.com/MM45/FV-XMSS-EC, master, ., conf...	7m 34s
Check EasyCrypt External Projects (xmss-fsai, https://github.com/MM45/FV-XMSS-EC, master, ., conf...	6m 47s
Check EasyCrypt External Projects (sphincsplus, https://github.com/MM45/FV-SPHINCSPLUS-EC, master...	20m 56s
Check EasyCrypt External Projects (set-status)	2s
Notification	3s
	1h 5m 53s

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