`PreservedSesquilinearForms` requires the module to be absolutely irreducible

[fingolfin]

gap> G:=Sp(4,5);
Sp(4,5)
gap> PreservedForms(Group(G.1));
Error, Currently the use of MeatAxe requires the module to be absolutely irreducible at GAPROOT/pkg/forms/lib/recognition.gi:902 called from
PreservedFormsOp( grp
 ) at GAPROOT/pkg/forms/lib/recognition.gi:962 called from
<function "PreservedForms for a matrix group over a finite field">( <arguments> )

At the very least this should be documented (maybe it is somewhere, but at least not when ?PreservedSesquilinearForms is checked).

[fingolfin]

It may be possible to remove this restriction when using a GAP with my patch gap-system/gap#5803 applied. Or even in any GAP version by just adapting what I did in my patch there.

@jdebeule any thoughts on this?