Update OpenTrafficPipeline.conf

Author: Chris Wiechmann

logstash/pipelines/OpenTrafficPipeline.conf

@@ -154,7 +154,7 @@ filter {
           code => '
             cacheAPINames = event.get("[@metadata][cacheAPIPerName]");
             apiRequestPath = event.get("[transactionSummary][path]");
-            if (cacheAPINames.nil?) 
+            if (cacheAPINames.nil? || cacheAPINames.empty?) 
               event.set("[@metadata][apiCacheKeyPrefix]", apiRequestPath);
               return;
             end