`TestSymplecticSubfieldSU(4, 17^2)` runs into error in `MagmaWithInversesByGenerators`

[fingolfin]

gap> TestSymplecticSubfieldSU(4, 17^2);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `MagmaWithInversesByGenerators' on 1 arguments at /Users/mhorn/Projekte/GAP/gap/lib/methsel2.g:250 called from
MagmaWithInversesByGenerators( gens ) at /Users/mhorn/Projekte/GAP/gap/lib/magma.gi:621 called from
SubgroupNC( Range( hom ), gens ) at /Users/mhorn/Projekte/GAP/gap/lib/ghom.gi:622 called from
ImagesSource( arg[1] ) at /Users/mhorn/Projekte/GAP/gap/lib/mapping.gi:106 called from
Image( Homom( ri )
 ) at /Users/mhorn/Projekte/GAP/repos/pkg/gap-packages/recog/gap/base/recognition.gi:547 called from
RecogniseGeneric( Group( List( GeneratorsOfGroup( H ), function ( x )
          return ImageElm( Homom( ri ), x );
      end ) ), methodsforimage( ri ), depthString, InitialDataForImageRecogNode( ri )
 ) at /Users/mhorn/Projekte/GAP/repos/pkg/gap-packages/recog/gap/base/recognition.gi:563 called from
...  at *stdin*:104
type 'quit;' to quit to outer loop

[fingolfin]

Also happens in e.g. TestSymplecticSubfieldSU(4, 17^2); or TestTensorInducedDecompositionStabilizerInSU(2, 2, 17^2);

I suspect this is closely related to issue #133 as here, too, Image(Homom(ri)) is involved.