Segmentation fault for scan / constrained optimization for diatomic molecules

[longdragoon]

xtb version: pre-compiled binary xtb-6.7.1-linux-x86_64

Describe the bug
When doing a scan / constrained optimization for diatomic molecules like H2 O2, the xtb program will execute till showing the ANCOPT SETUP and

generating ANC from exact Hessian ...
Using Lindh-Hessian (1995)

and then give the following error message:

forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image              PC                Routine            Line        Source             
xtb                000000000046E88A  Unknown               Unknown  Unknown
xtb                0000000002D1BD40  Unknown               Unknown  Unknown
xtb                000000000109EF48  xtb_detrotra_mp_d         141  detrotra.f90
xtb                0000000000FBB267  xtb_type_anc_mp_g         244  anc.f90
xtb                0000000000B14B06  xtb_optimizer_mp_         532  optimizer.f90
xtb                0000000000A2754E  xtb_geoopt_mp_geo         147  geoopt_driver.f90
xtb                000000000042AE6C  xtb_prog_main_mp_         832  main.F90
xtb                0000000000450EA2  MAIN__                     57  primary.f90
xtb                0000000000401E42  Unknown               Unknown  Unknown
xtb                0000000002D1298A  Unknown               Unknown  Unknown
xtb                0000000002D14227  Unknown               Unknown  Unknown
xtb                0000000000401D05  Unknown               Unknown  Unknown

To Reproduce

xtb --gfn 1 --opt extreme --input scan.inp --verbose h2_opt.xyz > scan.txt

scan.inp:

$constrain
 force constant=10.0
 distance: 1, 2, 0.7
$scan
 1: 0.7, 1.0, 31
$end

h2_opt.xyz:

2
 energy: -1.036708103979 gnorm: 0.000000077126 xtb: 6.7.1 (edcfbbe)
H            0.01720557368941       -0.00000009008817       -0.00000006005878
H            0.78279442629475       -0.00000409870203       -0.00000273246802

scan.txt

[foxtran]

Still can be reproduced with latest xtb version. I will fix it at morning.