Segfault / hand while running `&fraig`

[gadfort]

When attempting to run the default yosys script on this module, it hangs in the ``&fraig -x` call, when I manually add the verbose flag is segfaults.

It's been checked against the head of master.

+ &fraig -x 
Solver type = 2. Simulate 4 words in 10 rounds. SAT with 1000000 confs. Recycle after 500 SAT calls.
Sim    0 :   6.67 %  P =      0  D =      0  F =       0  cst =      926  cls =     640  lit =     2202   Time =     0.00 sec
Sim    1 :   4.11 %  P =      0  D =      0  F =       0  cst =      606  cls =     429  lit =     1355   Time =     0.00 sec
Sim    2 :   3.63 %  P =      0  D =      0  F =       0  cst =      554  cls =     386  lit =     1199   Time =     0.00 sec
Sim    3 :   3.50 %  P =      0  D =      0  F =       0  cst =      537  cls =     369  lit =     1156   Time =     0.00 sec
Sim    4 :   3.36 %  P =      0  D =      0  F =       0  cst =      512  cls =     358  lit =     1107   Time =     0.00 sec
Sim    5 :   2.05 %  P =      0  D =   2468  F =       0  cst =      355  cls =     245  lit =      677   Time =     0.09 sec
Segmentation fault (core dumped)

error.tar.gz

tar xvf error.tar.gz
cd error
abc -f abc.script

Ideally, this should not segfault or hang.

FYI: @QuantamHD