[GAP Forum] Understanding MatrixByBlockMatrix

[Anvita]

Dear Forum,

How can I avoid getting an error when trying to convert
a block matrix to an ordinary one in the following example?
If I enter "return;" in the break loop, I get a "segmentation fault"
followed by a crash of GAP session.

Thank you.
Anvita


z:=Z(4);
bm:=BlockMatrix(
   [[1,1,[[z]]],
    [2,2,[[z]]]],2,2);
Display(bm);
MatrixByBlockMatrix(bm);


gap> z:=Z(4);
Z(2^2)
gap>
gap> bm:=BlockMatrix(
>    [[1,1,[[z]]],
>     [2,2,[[z]]]],2,2);
<block matrix of dimensions (2*1)x(2*1)>
gap>
gap> Display(bm);
z = Z(4)
 z^1   .
   . z^1
gap>
gap> MatrixByBlockMatrix(bm);
Error, You cannot convert a locked vector compressed over GF(2) to GF(4) in
  mat{[ (i - 1) * blockmat!.rpb + 1 .. i * blockmat!.rpb ]}{
   [ (j - 1) * blockmat!.cpb + 1 .. j * blockmat!.cpb ]}
 := MatrixByBlockMatrix( block[3] ); called from
<function "unknown">( <arguments> )
 called from read-eval loop at line 17 of *stdin*
You can `return;' to ignore the conversion

brk> return;
Segmentation fault (core dumped)