Membership test for groups respecting a sesquilinear form fails for matrix objects #6671

gap> G := GU( 3, 2 );
GU(3,2)
gap> H := Group( List( GeneratorsOfGroup( G ),
>                   x -> Matrix( IsPlistMatrixRep, GF(4), x ) ) );
Group([ <immutable 3x3-matrix over GF(2^2)>, <immutable 3x3-matrix over GF(2^2)> ])
gap> r := ShallowCopy( InvariantSesquilinearForm( G ) );
rec( baseDomain := GF(2^2), matrix := [ [ 0*Z(2), 0*Z(2), Z(2)^0 ], [ 0*Z(2), Z(2)^0, 0*Z(2) ], [ Z(2)^0, 0*Z(2), 0*Z(2) ] ] )
gap> r.matrix := Matrix( IsPlistMatrixRep, GF(4), r.matrix );;
gap> r.matrix;
<3x3-matrix over GF(2^2)>
gap> SetInvariantSesquilinearForm( H, r );
gap> SetIsFullSubgroupGLorSLRespectingSesquilinearForm( H, true );
gap> GeneratorsOfGroup( H )[1] in H;
Error, <matobj> * <mat> is not defined
*[1] Error( "<matobj> * <mat> is not defined" );
   @ /home/peter/gap/gap-4.16.1/lib/matobj.gi:1167
 [2] mat * inv * List( TransposedMat( mat ), function ( row )
        return List( row, function ( x )
                return x ^ pow;
            end );
    end )
   @ /home/peter/gap/gap-4.16.1/lib/grpmat.gi:886
<function "in respecting sesquilinear form">( <arguments> )
 called from read-eval loop at *stdin*:9
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
brk> quit;
gap> H2 := Group( List( GeneratorsOfGroup( G ),
>                    x -> Matrix( IsPlistMatrixRep, GF(4), x ) ) );;
gap> SetInvariantSesquilinearForm( H2, r );;
gap> HasIsFullSubgroupGLorSLRespectingSesquilinearForm( H2 );
false
gap> GeneratorsOfGroup( H2 )[1] in H2;
true

gap> GeneratorsOfGroup( H2 )[1] in H2;
true