GenericException: java.lang.NullPointerException: element cannot be mapped to a null key

com.alibaba.dubbo.rpc.service.GenericException: java.lang.NullPointerException: element cannot be mapped to a null key
java.lang.NullPointerException: element cannot be mapped to a null key
at java.util.Objects.requireNonNull(Unknown Source)
at java.util.stream.Collectors.lambda$groupingBy$159(Unknown Source)
at java.util.stream.ReduceOps$3ReducingSink.accept(Unknown Source)
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(Unknown Source)
at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source)
at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
at java.util.stream.ReferencePipeline.collect(Unknown Source)
at com.pangu.project.manager.approval.impl.ProjectManagerImpl.page(ProjectManagerImpl.java:655)
at com.pangu.project.manager.approval.impl.ProjectManagerImpl$$FastClassBySpringCGLIB$$5887bc3d.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:684)
at com.pangu.project.manager.approval.impl.ProjectManagerImpl$$EnhancerBySpringCGLIB$$409c484c.page()
at com.pangu.project.manager.impl.AbstractProjectManager.queryProject(AbstractProjectManager.java:59)
at com.pangu.project.manager.impl.AbstractProjectManager$$FastClassBySpringCGLIB$$b643955e.invoke()
at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:749)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:100)
at com.pangu.common.validation.LoggerAspect.logger(LoggerAspect.java:57)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:644)
at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:633)
at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:175)
at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:93)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
at com.pangu.project.manager.impl.AbstractProjectManager$$EnhancerBySpringCGLIB$$3546b5a2.queryProject()
at com.pangu.project.manager.ProjectHandlerContext.queryProject(ProjectHandlerContext.java:34)

操作的元素存在为空的情况，对元素非空进行判断。