Make sure headers are not null

Author: acogoluegnes

src/main/java/com/rabbitmq/client/observation/micrometer/MicrometerObservationCollector.java

@@ -85,8 +85,9 @@ public void publish(
     } catch (IOException | AlreadyClosedException e) {
       observation.error(e);
       throw e;
+    } finally {
+      observation.stop();
     }
-    observation.stop();
   }
 
   @Override
@@ -105,12 +106,18 @@ public GetResponse basicGet(BasicGetCall call, String queue) {
     try {
       GetResponse response = call.get();
       if (response != null) {
+        Map<String, Object> headers;
+        if (response.getProps() == null || response.getProps().getHeaders() == null) {
+          headers = Collections.emptyMap();
+        } else {
+          headers = response.getProps().getHeaders();
+        }
         DeliverContext context =
             new DeliverContext(
                 response.getEnvelope().getExchange(),
                 response.getEnvelope().getRoutingKey(),
                 queue,
-                response.getProps().getHeaders(),
+                headers,
                 response.getBody() == null ? 0 : response.getBody().length);
         Observation observation =
             RabbitMqObservationDocumentation.RECEIVE_OBSERVATION.observation(

src/test/java/com/rabbitmq/client/test/functional/MicrometerObservationCollectorMetrics.java

@@ -191,7 +191,6 @@ public SampleTestRunnerConsumer yourCode() {
           consumeConnection = connectionFactory.newConnection();
           Channel basicGetChannel = consumeConnection.createChannel();
           waitAtMost(() -> basicGetChannel.basicGet(QUEUE, true) != null);
-
           waitAtMost(() -> buildingBlocks.getFinishedSpans().size() >= 3);
           System.out.println(
               buildingBlocks.getFinishedSpans().stream()