CodePcGroup fails for trivial pc group

[wilfwilson]

In today's master:

Observed behaviour

gap> G := TrivialGroup(IsPcGroup);
<pc group of size 1 with 0 generators>
gap> CodePcGroup(G);
Error, MaximumList: <list> must contain at least one element at /Users/Wilf/GAP/lib/list.gi:2596 called from
MaximumList( arg[1] ) at /Users/Wilf/GAP/lib/list.gi:2510 called from
Maximum( indices ) at /Users/Wilf/GAP/lib/randiso.gi:244 called from
CodePcgs( Pcgs( G ) ) at /Users/Wilf/GAP/lib/randiso.gi:294 called from
<function "CodePcGroup">( <arguments> )

Expected behaviour

gap> G := TrivialGroup(IsPcGroup);
<pc group of size 1 with 0 generators>
gap> CodePcGroup(G);
0

(Since PcGroupCode(0, 1) gives a trivial pc group, I'd guess this is the right code).

(Thanks for teaching me about CodePcGroup @fingolfin!)