Here is my proposed fix, inspired by purgeCentralCache:

diff --git a/lemonldap-ng-handler/example/scripts/purgeLocalCache b/lemonldap-ng-handler/example/scripts/purgeLocalCache
index f945dc52b..7929c7187 100755
--- a/lemonldap-ng-handler/example/scripts/purgeLocalCache
+++ b/lemonldap-ng-handler/example/scripts/purgeLocalCache
@@ -19,9 +19,14 @@ my $debug = 0;
 #=============================================================================
 my $lmconf = Lemonldap::NG::Common::Conf->new()
   or die $Lemonldap::NG::Common::Conf::msg;
-my $conf = $lmconf->getLocalConf(HANDLERSECTION)
+my $conf = $lmconf->getConf or die "Unable to get configuration ($!)";
+my $localconf = $lmconf->getLocalConf(HANDLERSECTION)
   or die "Unable to get local configuration ($!)";
 
+if ($localconf) {
+    $conf->{$_} = $localconf->{$_} foreach ( keys %$localconf );
+}
+
 print "Configuration loaded\n" if $debug;
 
 # Handler cache