Pickles: thread panicked while processing panic. aborting.

[dannywillems]

On develop (354f9d7), also in CI.
To reproduce:

cd src/lib/pickles
dune build @runtest

File "src/lib/snarky/src/base/backend_extended.ml", line 177, characters 4-300: project correctness (0.051 sec)
File "src/lib/snarky/src/base/utils.ml", line 288, characters 4-539: all (0.050 sec)
File "src/lib/snarky/src/base/snark0.ml", line 291, characters 6-685: is_square (0.000 sec)
File "src/lib/snarky/src/base/snark0.ml", line 572, characters 2-840: lt_bitstring_value (0.087 sec)
File "src/lib/snarky/src/base/backend_extended.ml", line 177, characters 4-300: project correctness (0.044 sec)
File "src/lib/snarky/src/base/utils.ml", line 288, characters 4-539: all (0.050 sec)
File "src/lib/snarky/src/base/snark0.ml", line 291, characters 6-685: is_square (0.000 sec)
File "src/lib/snarky/src/base/snark0.ml", line 572, characters 2-840: lt_bitstring_value (0.086 sec)
File "src/lib/snarky/snarky_curve/snarky_curve.ml", line 558, characters 2-2282: scale_fast (0.000 sec)
File "src/lib/pickles/wrap_main_inputs.ml", line 84, characters 0-139: sponge (0.002 sec)
File "src/lib/snarky/snarky_curve/snarky_curve.ml", line 558, characters 2-2282: scale_fast (0.000 sec)
thread panicked while processing panic. aborting.
0 tests ran, 0 test_modules ran   

[dannywillems]

Fixed by #14659