Don't bother to call applier if there are no roles

The applier logic also had a test for that, but since it is only
being called in one location, it made more sense to move the check
there.  Also, since no one is interested in the return value, don't
bother to set anything.

src/Perl6/Metamodel/ConcreteRoleHOW.nqp

@@ -77,7 +77,7 @@ class Perl6::Metamodel::ConcreteRoleHOW
 
             Perl6::Metamodel::Configuration.role_to_role_applier_type.apply(
               $target, @roles_to_compose
-            );
+            ) if nqp::elems(@roles_to_compose);
 
             my @role_typecheck_list := nqp::clone(@!role_typecheck_list);
             sub add_to_typecheck_list(@roles) {

src/Perl6/Metamodel/RoleToRoleApplier.nqp

@@ -2,9 +2,6 @@ my class RoleToRoleApplier {
     method apply($target, @roles) {
         my $HOW := $target.HOW;
 
-        # Ensure we actually have something to appply.
-        return nqp::list unless nqp::elems(@roles);
-
         # Aggregate all of the methods sharing names, eliminating
         # any duplicates (a method can't collide with itself).
         my %meth_info;
@@ -15,6 +12,7 @@ my class RoleToRoleApplier {
         my %priv_meth_providers;
         my $with_submethods := $HOW.language_revision < 3; # less than 6.e
         my $submethod_type := Perl6::Metamodel::Configuration.submethod_type;
+
         for @roles {
             my $role := $_;
             sub build_meth_info(@methods, @meth_names, %meth_info_to_use, @meth_names_to_use, %meth_providers_to_use) {
@@ -299,8 +297,6 @@ my class RoleToRoleApplier {
                 }
             }
         }
-
-        1;
     }
 
     Perl6::Metamodel::Configuration.set_role_to_role_applier_type(RoleToRoleApplier);