NPE on DefaultApplications.getEnvironments

从 ApplicationEnvironments.java 中的 Builder.putAllUserProvided 和 userProvided 开始，然后跟踪报告行中从 DefaultApplications.toApplicationEnvironments 和 getEnvironments 进行的转换。使用没有用户提供的环境变量的应用程序重现该情况；当 getEnvironments 完成且没有 NullPointerException 时即表示完成。

Hi,

I got a NullPointerException when using DefaultApplications.getEnvironments:

Exception in thread "main" java.lang.NullPointerException
	at org.cloudfoundry.operations.applications.ApplicationEnvironments$Builder.putAllUserProvided(ApplicationEnvironments.java:346)
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Assembly trace from producer [reactor.core.publisher.MonoMapFuseable] :
	reactor.core.publisher.Mono.checkpoint(Mono.java:1902)
	org.cloudfoundry.operations.applications.DefaultApplications.getEnvironments(DefaultApplications.java:300)
Error has been observed at the following site(s):
	|_ Mono.checkpoint ⇢ at org.cloudfoundry.operations.applications.DefaultApplications.getEnvironments(DefaultApplications.java:300)
Stack trace:
		at org.cloudfoundry.operations.applications.ApplicationEnvironments$Builder.putAllUserProvided(ApplicationEnvironments.java:346)
		at org.cloudfoundry.operations.applications.ApplicationEnvironments$Builder.userProvided(ApplicationEnvironments.java:337)
		at org.cloudfoundry.operations.applications.DefaultApplications.toApplicationEnvironments(DefaultApplications.java:1763)
		at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:113)
		at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1789)
		at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249)
		at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1789)
		at reactor.core.publisher.MonoFlatMap$FlatMapInner.onNext(MonoFlatMap.java:249)
		at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1789)
		at reactor.core.publisher.MonoSingle$SingleSubscriber.onComplete(MonoSingle.java:185)
		at reactor.core.publisher.FluxFlatMap$FlatMapMain.checkTerminated(FluxFlatMap.java:845)
		at reactor.core.publisher.FluxFlatMap$FlatMapMain.drainLoop(FluxFlatMap.java:607)
		at reactor.core.publisher.FluxFlatMap$FlatMapMain.innerComplete(FluxFlatMap.java:916)
		at reactor.core.publisher.FluxFlatMap$FlatMapInner.onComplete(FluxFlatMap.java:1020)
		at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142)
		at reactor.core.publisher.FluxHandle$HandleSubscriber.onComplete(FluxHandle.java:212)
		at reactor.core.publisher.FluxMap$MapConditionalSubscriber.onComplete(FluxMap.java:269)
		at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onComplete(FluxDoFinally.java:145)
		at reactor.core.publisher.FluxHandleFuseable$HandleFuseableSubscriber.onComplete(FluxHandleFuseable.java:229)
		at reactor.core.publisher.FluxContextWrite$ContextWriteSubscriber.onComplete(FluxContextWrite.java:126)
		at reactor.core.publisher.Operators$MonoSubscriber.complete(Operators.java:1790)
		at reactor.core.publisher.MonoCollectList$MonoCollectListSubscriber.onComplete(MonoCollectList.java:128)
		at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:259)
		at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142)
		at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onComplete(FluxDoFinally.java:145)
		at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:142)
		at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:389)
		at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:396)
		at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:452)
		at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:664)
		at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
		at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
		at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436)
		at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
		at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
		at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
		at io.netty.handler.logging.LoggingHandler.channelRead(LoggingHandler.java:271)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
		at io.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:1533)
		at io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1282)
		at io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1329)
		at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:508)
		at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:447)
		at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
		at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
		at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
		at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
		at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
		at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:719)
		at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:655)
		at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:581)
		at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
		at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
		at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
		at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
		at java.base/java.lang.Thread.run(Thread.java:834)

It seems to happen on an application without user provided environment variables.