Exception creating DefaultImageJUIService

[From](https://gitter.im/scenerygraphics/SciView?at=5d94aeb39d4cf1736057daa6) @skalarproduktraum:

```
java.lang.IllegalArgumentException: Invalid service: net.imagej.ui.DefaultImageJUIService

at org.scijava.service.ServiceHelper.createExactService(ServiceHelper.java:281)
at org.scijava.service.ServiceHelper.loadService(ServiceHelper.java:232)
at org.scijava.service.ServiceHelper.loadService(ServiceHelper.java:195)
at org.scijava.service.ServiceHelper.loadServices(ServiceHelper.java:167)
at org.scijava.Context.(Context.java:281)
at org.scijava.Context.(Context.java:237)
at org.scijava.Context.(Context.java:133)
at org.scijava.Context.(Context.java:120)
at org.scijava.Context.(Context.java:109)
at graphics.scenery.repl.REPL.(REPL.kt:33)
at graphics.scenery.SceneryBase.main(SceneryBase.kt:196)
at graphics.scenery.tests.examples.basic.SponzaExample.main(SponzaExample.kt:107)
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:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.scijava.NullContextException: Before attempting to use this object, please set its context by calling the setContext(...) method.
at org.scijava.AbstractContextual.context(AbstractContextual.java:58)
at org.scijava.service.Service.registerEventHandlers(Service.java:68)
at org.scijava.service.ServiceHelper.createServiceRecursively(ServiceHelper.java:355)
at org.scijava.service.ServiceHelper.createExactService(ServiceHelper.java:270)
... 33 more
```

Start with the failing initialization path in graphics.scenery.repl.REPL at REPL.kt:33 and graphics.scenery.SceneryBase at SceneryBase.kt:196, then inspect the ServiceHelper and Context frames in the stack trace. Reproduce the SponzaExample JUnit failure and determine what must change so DefaultImageJUIService initializes without the Invalid service and NullContextException.

Written by the indexing model from the issue text.