Custom loss function with DL4J UIServer error

dl4juiservergist.txt

18:17:08.937 [application-akka.actor.default-dispatcher-4] ERROR application - 

! @766o9k5ib - Internal server error, for (GET) [/train/model/graph] ->
 
play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[InvocationTargetException: null]]
	at play.api.http.HttpErrorHandlerExceptions$.throwableToUsefulException(HttpErrorHandler.scala:265)
	at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:191)
	at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:151)
	at play.core.server.netty.PlayDefaultUpstreamHandler$$anonfun$9$$anonfun$apply$1.applyOrElse(PlayDefaultUpstreamHandler.scala:148)
	at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:33)
	at scala.util.Failure$$anonfun$recover$1.apply(Try.scala:185)
	at scala.util.Try$.apply(Try.scala:161)
	at scala.util.Failure.recover(Try.scala:185)
	at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324)
	at scala.concurrent.Future$$anonfun$recover$1.apply(Future.scala:324)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
	at play.api.libs.iteratee.Execution$trampoline$.executeScheduled(Execution.scala:109)
	at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:71)
	at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:40)
	at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:248)
	at scala.concurrent.Promise$class.complete(Promise.scala:55)
	at scala.concurrent.impl.Promise$DefaultPromise.complete(Promise.scala:153)
	at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:23)
	at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:40)
	at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:397)
	at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
	at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
	at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
	at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
Caused by: java.lang.reflect.InvocationTargetException: null
	at sun.reflect.GeneratedMethodAccessor12.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at play.routing.RouterBuilderHelper$$anonfun$build$1$$anonfun$apply$1$$anonfun$5.apply(RouterBuilderHelper.scala:66)
	at play.routing.RouterBuilderHelper$$anonfun$build$1$$anonfun$apply$1$$anonfun$5.apply(RouterBuilderHelper.scala:62)
	at play.api.mvc.Action$.invokeBlock(Action.scala:533)
	at play.api.mvc.Action$.invokeBlock(Action.scala:530)
	at play.api.mvc.ActionBuilder$$anon$1.apply(Action.scala:493)
	at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105)
	at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4$$anonfun$apply$5.apply(Action.scala:105)
	at play.utils.Threads$.withContextClassLoader(Threads.scala:21)
	at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:104)
	at play.api.mvc.Action$$anonfun$apply$1$$anonfun$apply$4.apply(Action.scala:103)
	at scala.Option.map(Option.scala:145)
	at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:103)
	at play.api.mvc.Action$$anonfun$apply$1.apply(Action.scala:96)
	at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524)
	at play.api.libs.iteratee.Iteratee$$anonfun$mapM$1.apply(Iteratee.scala:524)
	at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560)
	at play.api.libs.iteratee.Iteratee$$anonfun$flatMapM$1.apply(Iteratee.scala:560)
	at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536)
	at play.api.libs.iteratee.Iteratee$$anonfun$flatMap$1$$anonfun$apply$13.apply(Iteratee.scala:536)
	at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
	at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
	... 6 common frames omitted
Caused by: java.lang.NullPointerException: null
	at org.deeplearning4j.ui.module.train.TrainModuleUtils.buildGraphInfo(TrainModuleUtils.java:231)
	at org.deeplearning4j.ui.module.train.TrainModule.getGraphInfo(TrainModule.java:611)
	at org.deeplearning4j.ui.module.train.TrainModule.getModelGraph(TrainModule.java:594)
	at org.deeplearning4j.ui.module.train.TrainModule$$Lambda$23/1222293761.get(Unknown Source)
	at org.deeplearning4j.ui.play.misc.FunctionUtil$$Lambda$14/1250119072.apply(Unknown Source)
	... 30 common frames omitted