Fix piwik/matomo call

Change-Id: I712ddff1b9e0728ca0640c4266f05b643009fcd2
diff --git a/script/derekovecs-server b/script/derekovecs-server
index faf579a..3531910 100755
--- a/script/derekovecs-server
+++ b/script/derekovecs-server
@@ -343,7 +343,7 @@
          return $str;
       });
 
-if(app->config->{Piwik} && app->config->{Piwik}->url) {
+if(app->config->{Piwik} && app->config->{Piwik}->{url}) {
   hook(
       after_render => sub {
         my $c = shift;