app-layer: only register flow counter for detection-only

Other counters are never incremented if no parser is active.

src/app-layer.c

@@ -1326,6 +1326,9 @@ void AppLayerRegisterThreadCounters(ThreadVars *tv)
                 applayer_counters[alproto][ipproto_map].counter_id =
                         StatsRegisterCounter(applayer_counter_names[alproto][ipproto_map].name, tv);
 
+                if (AppLayerParserProtoIsRegistered(ipproto, alproto) != 1)
+                    continue;
+
                 applayer_counters[alproto][ipproto_map].counter_tx_id = StatsRegisterCounter(
                         applayer_counter_names[alproto][ipproto_map].tx_name, tv);