[Bug]: AutoRebalance to remove brokers failed because of kafkaRebalanceState is null

[acgtun]

Bug Description

2025-10-12 04:08:10 INFO  KafkaAutoRebalancingReconciler:148 - Reconciliation #107345(watch) Kafka(kafka/preprod): Auto-rebalance on scaling down with KafkaRebalance kafka/preprod-auto-rebalancing- │
│ 2025-10-12 04:08:10 ERROR AbstractOperator:285 - Reconciliation #107345(watch) Kafka(kafka/preprod): createOrUpdate failed                                                                            │
│ java.lang.NullPointerException: Cannot invoke "io.strimzi.api.kafka.model.rebalance.KafkaRebalanceState.ordinal()" because "kafkaRebalanceState" is null                                              │
│     at io.strimzi.operator.cluster.operator.assembly.KafkaAutoRebalancingReconciler.lambda$onRebalanceOnScaleDown$8(KafkaAutoRebalancingReconciler.java:152) ~[io.strimzi.cluster-operator-0.47.0.jar │
│     at io.vertx.core.impl.future.Composition.complete(Composition.java:40) ~[io.vertx.vertx-core-5.0.1.jar:5.0.1]                                                                                     │
│     at io.vertx.core.impl.future.FutureBase.lambda$emitResult$0(FutureBase.java:59) ~[io.vertx.vertx-core-5.0.1.jar:5.0.1]                                                                            │
│     at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:148) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                    │
│     at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:141) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                │
│     at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:507) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                        │
│     at io.netty.channel.SingleThreadIoEventLoop.run(SingleThreadIoEventLoop.java:182) ~[io.netty.netty-transport-4.2.2.Final.jar:4.2.2.Final]                                                         │
│     at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:1073) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                             │
│     at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                                 │
│     at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                     │
│     at java.lang.Thread.run(Thread.java:840) ~[?:?]                                                                                                                                                   │
│ 2025-10-12 04:08:10 WARN  AbstractOperator:566 - Reconciliation #107345(watch) Kafka(kafka/preprod): Failed to reconcile                                                                              │
│ java.lang.NullPointerException: Cannot invoke "io.strimzi.api.kafka.model.rebalance.KafkaRebalanceState.ordinal()" because "kafkaRebalanceState" is null                                              │
│     at io.strimzi.operator.cluster.operator.assembly.KafkaAutoRebalancingReconciler.lambda$onRebalanceOnScaleDown$8(KafkaAutoRebalancingReconciler.java:152) ~[io.strimzi.cluster-operator-0.47.0.jar │
│     at io.vertx.core.impl.future.Composition.complete(Composition.java:40) ~[io.vertx.vertx-core-5.0.1.jar:5.0.1]                                                                                     │
│     at io.vertx.core.impl.future.FutureBase.lambda$emitResult$0(FutureBase.java:59) ~[io.vertx.vertx-core-5.0.1.jar:5.0.1]                                                                            │
│     at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:148) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                    │
│     at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:141) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                │
│     at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:507) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                        │
│     at io.netty.channel.SingleThreadIoEventLoop.run(SingleThreadIoEventLoop.java:182) ~[io.netty.netty-transport-4.2.2.Final.jar:4.2.2.Final]                                                         │
│     at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:1073) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                             │
│     at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                                 │
│     at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[io.netty.netty-common-4.2.2.Final.jar:4.2.2.Final]                                                     │
│     at java.lang.Thread.run(Thread.java:840) ~[?:?]

Steps to reproduce

1. enable autoRealance for remove-broker
2. reduce kafkanodepool broker from 20 nodes to 10 nodes

Expected behavior

No response

Strimzi version

0.47.0

Kubernetes version

Client Version: v1.29.12 Server Version: v1.30.3

Installation method

argoCD

Infrastructure

kubernetes cluster

Configuration files and logs

No response

Additional context

Actually, the data was already moved out by cruise-control, but the partitions were not moved out. Later, I manually run a reassignment command to assign replicas to other brokers (0 to 9), after that, the AutoRebalance immediately remove broker 10 to 19.