NPE on Spring Boot

[mp911de]

java.lang.NullPointerException
at biz.paluch.logging.gelf.log4j.Log4jLogEvent.getAllMdcNames(Log4jLogEvent.java:155)
at biz.paluch.logging.gelf.log4j.Log4jLogEvent.getMdcNames(Log4jLogEvent.java:174)
at biz.paluch.logging.gelf.MdcGelfMessageAssembler.createGelfMessage(MdcGelfMessageAssembler.java:39)
at biz.paluch.logging.gelf.log4j.GelfLogAppender.createGelfMessage(GelfLogAppender.java:124)
at biz.paluch.logging.gelf.log4j.GelfLogAppender.append(GelfLogAppender.java:88)
at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:251)
at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:66)
at org.apache.log4j.Category.callAppenders(Category.java:206)
at org.apache.log4j.Category.forcedLog(Category.java:391)
at org.apache.log4j.Category.log(Category.java:856)
at org.slf4j.impl.Log4jLoggerAdapter.log(Log4jLoggerAdapter.java:601)
at org.apache.commons.logging.impl.SLF4JLocationAwareLog.info(SLF4JLocationAwareLog.java:159)
at org.springframework.boot.StartupInfoLogger.logStarting(StartupInfoLogger.java:52)
at org.springframework.boot.SpringApplication.logStartupInfo(SpringApplication.java:583)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:308)
at de.paluch.heckenlights.Application.main(Application.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:53)
at java.lang.Thread.run(Thread.java:745)