Merge pull request #1529 from vincz777/vincz777-patch-1

Fix NPE in MetricsChatModelListener.java

Author: geoand

core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/listeners/MetricsChatModelListener.java

@@ -76,7 +76,10 @@ public void onResponse(ChatModelResponseContext responseContext) {
 
         ChatRequest request = responseContext.chatRequest();
         ChatResponse response = responseContext.chatResponse();
-        Tags tags = Tags.of("gen_ai.request.model", request.parameters().modelName());
+        Tags tags = Tags.empty();
+        if (request.parameters().modelName() != null) {
+            tags = tags.and("gen_ai.request.model", request.parameters().modelName());
+        }
         if (response.metadata().modelName() != null) {
             tags = tags.and("gen_ai.response.model", response.metadata().modelName());
         }