IsomorphismGroups regression in 4.13.0

[antonio-rojas]

Observed behaviour

With 4.13.0 or current master:

gap> G:=Group([ (2,11,20)(3,10,19)(4,9,12)(5,8,13)(6,15,17)(7,14,18), (2,20)(3,4)(5,7)(8,18)(9,19)(10,12)(13,14)(15,17), (1,2)(3,20)(6,18)(7,19)(8,12)(9,11)(13,15)(16,17) ]);
Group([ (2,11,20)(3,10,19)(4,9,12)(5,8,13)(6,15,17)(7,14,18), (2,20)(3,4)(5,7)(8,18)(9,19)(10,12)(13,14)(15,17), (1,2)(3,20)(6,18)(7,19)(8,12)(9,11)
  (13,15)(16,17) ])
gap> H:=Group([ (1,2,3,4,5), (3,4,5), (6,7) ]);
Group([ (1,2,3,4,5), (3,4,5), (6,7) ])
gap> IsomorphismGroups(G,H);

Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `Representative' on 1 arguments
The 1st argument is 'fail' which might point to an earlier problem
 at /usr/share/gap/lib/methsel2.g:250 called from
Representative( of ) at /usr/share/gap/lib/morpheus.gi:538 called from
AssignNiceMonomorphismAutomorphismGroup( A, G ); at /usr/share/gap/lib/morpheus.gi:2565 called from
NiceMonomorphism( obj1 ) at /usr/share/gap/lib/grpnice.gi:313 called from
ClosureGroup( G, gen ) at /usr/share/gap/lib/grp.gi:2617 called from
ClosureGroup( G, obj ) at /usr/share/gap/lib/grp.gi:2644 called from
...  at *stdin*:3

Expected behaviour

With 4.12.2:

gap> G:=Group([ (2,11,20)(3,10,19)(4,9,12)(5,8,13)(6,15,17)(7,14,18), (2,20)(3,4)(5,7)(8,18)(9,19)(10,12)(13,14)(15,17), (1,2)(3,20)(6,18)(7,19)(8,12)(9,11)(13,15)(16,17) ]);
Group([ (2,11,20)(3,10,19)(4,9,12)(5,8,13)(6,15,17)(7,14,18), (2,20)(3,4)(5,7)(8,18)(9,19)(10,12)(13,14)(15,17), (1,2)(3,20)(6,18)(7,19)(8,12)(9,11)
  (13,15)(16,17) ])
gap> H:=Group([ (1,2,3,4,5), (3,4,5), (6,7) ]);
Group([ (1,2,3,4,5), (3,4,5), (6,7) ])
gap> IsomorphismGroups(G,H);

[ (2,11,20)(3,10,19)(4,9,12)(5,8,13)(6,15,17)(7,14,18), (2,20)(3,4)(5,7)(8,18)(9,19)(10,12)(13,14)(15,17), (1,2)(3,20)(6,18)(7,19)(8,12)(9,11)(13,
    15)(16,17) ] -> [ (1,2,3), (1,3)(4,5)(6,7), (2,5)(3,4)(6,7) ]

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[antonio-rojas]

Caused by 58f31c6

[fingolfin]

Thanks for the report @antonio-rojas we'll have a look

(Ping @hulpke)

[hulpke]

Fixed (harmless bug, will only lead to error messages).