--- gap/basic/grphoms.gi.orig 2020-07-24 17:55:13.000000000 -0600
+++ gap/basic/grphoms.gi 2022-09-11 10:29:16.792073715 -0600
@@ -158,6 +158,10 @@ function( hom )
gens := hom!.igs_gens_to_imgs[1];
imgs := hom!.igs_gens_to_imgs[2];
+ if Length(gens) = 0 then
+ return true;
+ fi;
+
# check relators
for i in [1..Length( gens )] do
if RelativeOrderPcp( gens[i] ) > 0 then
@@ -216,6 +220,10 @@ function( hom )
C := TrivialSubgroup(Range(hom)); # the cokernel
+ if Length(gens) = 0 then
+ return C;
+ fi;
+
# check relators
for i in [1..Length( gens )] do
if RelativeOrderPcp( gens[i] ) > 0 then