Trivial monoid becomes a group...

Issue #36 resolved
Attila Egri-Nagy
created an issue

...which is of course sensible, but it causes trouble since some semigroup methods may not work. Here is an example:

gap> S := Semigroup(IdentityTransformation(4));
gap> SmallGeneratingSet(S);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `SemigroupByGenerators' on 1 arguments called from
SemigroupByGenerators( arg ) called from
Semigroup( Generators( s ), rec(
    small := true ) ) called from
<function "unknown">( <arguments> )
 called from read-eval loop at line 7 of *stdin*
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue

This is just an example of this recurring problem. This makes processing a list of semigroups very difficult, as one has to check for the trivial monoid. The problem is there in 1.2.

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