IsStack needs to be unbound to be compatible with GAP 4.12

[hungaborhorvath]

IsStack seems to be a bound variable in gap 4.12, and that prevents subsemi to be loaded.

ghorvath@SamsungLaptop:~$ gap
 ┌───────┐   GAP 4.12.0 of 2022-08-18
 │  GAP  │   https://www.gap-system.org
 └───────┘   Architecture: x86_64-pc-linux-gnu-default64-kv8
 Configuration:  gmp 6.1.2, GASMAN, readline
 Loading the library and packages ...
 Packages:   AClib 1.3.2, Alnuth 3.2.1, AtlasRep 2.1.4, AutoDoc 2022.07.10, AutPGrp 1.11, Browse 1.8.14, CaratInterface 2.3.4, CRISP 1.4.5, Cryst 4.1.25, CrystCat 1.1.10, CTblLib 1.3.4, 
             FactInt 1.6.3, FGA 1.4.0, Forms 1.2.8, GAPDoc 1.6.6, genss 1.6.7, IO 4.7.2, IRREDSOL 1.4.3, LAGUNA 3.9.5, orb 4.8.5, Polenta 1.3.10, Polycyclic 2.16, PrimGrp 3.4.2, RadiRoot 2.9, 
             recog 1.3.2, ResClasses 4.7.3, SmallGrp 1.5, Sophus 1.27, SpinSym 1.5.2, TomLib 1.2.9, TransGrp 3.6.3, utils 0.76
 Try '??help' for help. See also '?copyright', '?cite' and '?authors'
gap> LoadPackage("subsemi");
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Loading  datastructures 0.2.7 (datastructures - GAP Data Structures)
by Markus Pfeiffer (http://www.morphism.de/~markusp),
   Max Horn (https://www.quendi.de/math),
   Christopher Jefferson (http://caj.host.cs.st-andrews.ac.uk/), and
   Steve Linton (http://sl4.host.cs.st-andrews.ac.uk/).
Homepage: https://gap-packages.github.io/datastructures
Report issues at https://github.com/gap-packages/datastructures/issues
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Loading  ferret 1.0.8 (Backtrack Search in Permutation Groups)
by Christopher Jefferson (https://caj.host.cs.st-andrews.ac.uk/).
Homepage: https://gap-packages.github.io/ferret/
Report issues at https://github.com/gap-packages/ferret/issues
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
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Loading  images 1.3.1 (Minimal and Canonical images)
by Christopher Jefferson (http://caj.host.cs.st-andrews.ac.uk/),
   Markus Pfeiffer (http://www.morphism.de/~markusp/),
   Rebecca Waldecker (http://conway1.mathematik.uni-halle.de/~waldecker/), and
   Eliza Jonauskyte ([email protected]).
maintained by:
   Christopher Jefferson (http://caj.host.cs.st-andrews.ac.uk/).
Homepage: https://gap-packages.github.io/images/
Report issues at https://github.com/gap-packages/images/issues
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
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Loading  GRAPE 4.8.5 (GRaph Algorithms using PErmutation groups)
by Leonard H. Soicher (http://www.maths.qmul.ac.uk/~lsoicher/).
Homepage: https://gap-packages.github.io/grape
Report issues at https://github.com/gap-packages/grape/issues
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
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Loading  Digraphs 1.5.3 (Digraphs - Methods for digraphs)
by Jan De Beule (http://homepages.vub.ac.be/~jdbeule/),
   Julius Jonusas (http://julius.jonusas.work),
   James Mitchell (https://jdbm.me),
   Maria Tsalakou (https://mariatsalakou.github.io/),
   Wilf A. Wilson (https://wilf.me), and
   Michael Young (https://mct25.host.cs.st-andrews.ac.uk).
with contributions by:
   Marina Anagnostopoulou-Merkouri ([email protected]),
   Finn Buck ([email protected]),
   Stuart Burrell ([email protected]),
   Reinis Cirpons ([email protected]),
   Tom Conti-Leslie ([email protected]),
   Luke Elliott ([email protected]),
   Ewan Gilligan ([email protected]),
   Samantha Harper ([email protected]),
   Max Horn (https://www.quendi.de/math),
   Christopher Jefferson (https://caj.host.cs.st-andrews.ac.uk),
   Markus Pfeiffer (https://www.morphism.de/~markusp),
   Lea Racine ([email protected]),
   Christopher Russell ([email protected]),
   Finn Smith ([email protected]),
   Ben Spiers ([email protected]), and
   Murray Whyte ([email protected]).
maintained by:
   James Mitchell (https://jdbm.me) and
   Wilf A. Wilson (https://wilf.me).
Homepage: https://digraphs.github.io/Digraphs
Report issues at https://github.com/digraphs/Digraphs/issues
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
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Loading  Semigroups 5.0.2
by James Mitchell (https://jdbm.me)
with contributions by:
     Marina Anagnostopoulou-Merkouri (https://github.com/marinaanagno),
     Stuart Burrell (https://stuartburrell.github.io),
     Reinis Cirpons (https://reinisc.id.lv/),
     Tom Conti-Leslie (https://tomcontileslie.com/),
     Joe Edwards (https://github.com/Joseph-Edwards),
     Attila Egri-Nagy (http://www.egri-nagy.hu),
     Luke Elliott (https://le27.github.io/Luke-Elliott/),
     Fernando Flores Brito (https://github.com/ffloresbrito),
     Nick Ham (https://n-ham.github.io),
     Robert Hancock (https://sites.google.com/view/robert-hancock/),
     Max Horn (https://www.quendi.de/math),
     Christopher Jefferson (https://caj.host.cs.st-andrews.ac.uk/),
     Julius Jonusas (http://julius.jonusas.work),
     Chinmaya Nagpal,
     Olexandr Konovalov (https://www.st-andrews.ac.uk/computer-science/people/obk1/),
     Artemis Konstantinidi,
     Dima V. Pasechnik (http://users.ox.ac.uk/~coml0531/),
     Markus Pfeiffer (https://www.morphism.de/~markusp/),
     Christopher Russell,
     Jack Schmidt (https://www.ms.uky.edu/~jack/),
     Sergio Siccha,
     Finn Smith (https://flsmith.github.io/),
     Ben Spiers,
     Nicolas Thiéry (https://nicolas.thiery.name/),
     Maria Tsalakou (https://mariatsalakou.github.io/),
     Murray Whyte,
     Wilf A. Wilson (https://wilf.me),
 and Michael Young (https://mtorpey.github.io/).
-----------------------------------------------------------------------------
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Loading  SgpDec 0.9.4 (Hierarchical Decompositions and Coordinate Systems)
by Attila Egri-Nagy (http://www.egri-nagy.hu),
   Chrystopher L. Nehaniv (http://homepages.feis.herts.ac.uk/~comqcln/), and
   J. D. Mitchell (http://tinyurl.com/jdmitchell).
maintained by:
   Attila Egri-Nagy (http://www.egri-nagy.hu) and
   J. D. Mitchell (http://tinyurl.com/jdmitchell).
Homepage: https://gap-packages.github.io/sgpdec/
Report issues at https://github.com/gap-packages/sgpdec/issues
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
Error, BIND_GLOBAL: variable `IsStack' must be unbound at /home/ghorvath/work/gap-4.12.0/lib/global.g:138 called from
BIND_GLOBAL( arg[1], CALL_FUNC_LIST( NewCategory, arg ) ); at /home/ghorvath/work/gap-4.12.0/lib/type.g:120 called from
<function "DeclareCategory">( <arguments> )
 called from read-eval loop at /home/ghorvath/work/gap-4.12.0/pkg/subsemi-0.76//lib/storage/stack.gd:10
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk> 

[hungaborhorvath]

Relevant for 4.12.1, as well.