PQuotient throwing error for large groups #5809
Description
The issue was encountered in conjuction with the package LINS in gap-packages/LINS#67.
The way I would like pQuotient to behave is the following. If I want to search for a p-class c up to order p^logord, and if there is none to be found, I would like the function to return fail. Currently it throws an error instead, which is bad as this function is called as a subroutine in LINS.
Example:
gap> F := FreeGroup(["a", "b"]);;
gap> a := F.1;;
gap> b := F.1;;
gap> p := 5;;
gap> G := F / [a^p, b^p, Comm(a,b)];
<fp group on the generators [ a, b ]>
gap> PQuotient(G, p, 1, 2);
<5-quotient system of 5-class 1 with 2 generators>
gap> PQuotient(G, p, 1, 1); # throws error, since we need two generators
Error, List Elements: <list>[2] must have an assigned value in
qs!.images{generators} := gens{[ 1 .. d ]}; at /Users/friedrich/.gap/gapdev/lib/pquot.gi:1345 called from
AbelianPQuotient( qs ); at /Users/friedrich/.gap/gapdev/lib/pquot.gi:1456 called from
<function "PQuotient">( <arguments> )
called from read-eval loop at *stdin*:19
type 'quit;' to quit to outer loop
brk>
Since I am not sure, why it was designed to throw an error instead of fail, I wanted to ask if there are good reasons for this behaviour. If not, I volunteer to change the behaviour, I think it should be fairly easy by just checking if we try to insert too many generators into the list. But I might be wrong.