fix NPE when getting native thread id (#15301)

This commit adds null guard to get the native thread when constructing pipeline report

Fix: #15300
(cherry picked from commit cd78558)

logstash-core/src/main/java/org/logstash/execution/PipelineReporterExt.java

@@ -37,6 +37,7 @@
 import org.logstash.config.ir.compiler.AbstractOutputDelegatorExt;
 
 import java.util.Collection;
+import java.util.Optional;
 
 /**
  * JRuby extension
@@ -161,7 +162,7 @@ private RubyArray workerStates(final ThreadContext context, final RubyHash batch
         final RubyArray result = context.runtime.newArray();
         ((Iterable<IRubyObject>) pipeline.callMethod(context, "worker_threads"))
             .forEach(thread -> {
-                final long nativeThreadId = ((RubyThread) thread).getNativeThread().getId();
+
                 final RubyHash hash = RubyHash.newHash(context.runtime);
                 IRubyObject status = thread.callMethod(context, "status");
                 if (status.isNil()) {
@@ -170,8 +171,15 @@ private RubyArray workerStates(final ThreadContext context, final RubyHash batch
                 hash.op_aset(context, STATUS_KEY, status);
                 hash.op_aset(context, ALIVE_KEY, thread.callMethod(context, "alive?"));
                 hash.op_aset(context, INDEX_KEY, context.runtime.newFixnum(result.size()));
-                final IRubyObject batch = batchMap.op_aref(context, context.runtime.newFixnum(nativeThreadId));
-                hash.op_aset(context, INFLIGHT_COUNT_KEY, extractBatchSize(context, batch));
+
+                IRubyObject batchSize = Optional.of((RubyThread) thread)
+                        .map(RubyThread::getNativeThread)
+                        .map(Thread::getId)
+                        .map(id -> batchMap.op_aref(context, context.runtime.newFixnum(id)))
+                        .map(batch -> extractBatchSize(context, batch))
+                        .orElse(context.runtime.newFixnum(0L));
+
+                hash.op_aset(context, INFLIGHT_COUNT_KEY, batchSize);
                 result.add(hash);
             });
         return result;