Debugging MethodHandle creation, I am getting:

Exception in thread "main" java.lang.NullPointerException
at jdk.nashorn.internal.runtime.RecompilableScriptFunctionData.toString(RecompilableScriptFunctionData.java:134)
at java.lang.String.valueOf(String.java:2979)
at java.lang.StringBuilder.append(StringBuilder.java:131)
at jdk.nashorn.internal.lookup.MethodHandleFactory$TraceMethodHandleFunctionality.describe(MethodHandleFactory.java:458)
at jdk.nashorn.internal.lookup.MethodHandleFactory$TraceMethodHandleFunctionality.describe(MethodHandleFactory.java:454)
at jdk.nashorn.internal.lookup.MethodHandleFactory$TraceCreateMethodHandleFunctionality.debug(MethodHandleFactory.java:641)
at jdk.nashorn.internal.lookup.MethodHandleFactory$TraceMethodHandleFunctionality.insertArguments(MethodHandleFactory.java:497)
at jdk.nashorn.internal.runtime.ScriptFunction.getFunctionGuard(ScriptFunction.java:591)
at jdk.nashorn.internal.runtime.ScriptFunction.findCallMethod(ScriptFunction.java:552)
at jdk.nashorn.internal.runtime.ScriptObject.lookup(ScriptObject.java:1650)
at jdk.nashorn.internal.runtime.linker.NashornLinker.getGuardedInvocation(NashornLinker.java:92)
at jdk.internal.dynalink.support.CompositeTypeBasedGuardingDynamicLinker.getGuardedInvocation(CompositeTypeBasedGuardingDynamicLinker.java:176)
at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:138)
at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:232)
at jdk.nashorn.internal.scripts.Script$init._L65(jar:file:/Users/jfdenise/workspaces/avatar.js/avatar.js/dist/avatar-js.jar!/net/java/avatar/js/init.js:146)
at jdk.nashorn.internal.scripts.Script$init.runScript(jar:file:/Users/jfdenise/workspaces/avatar.js/avatar.js/dist/avatar-js.jar!/net/java/avatar/js/init.js:65)
at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:498)
at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:207)
at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:378)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:544)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:526)
at jdk.nashorn.api.scripting.NashornScriptEngine.evalImpl(NashornScriptEngine.java:522)
at jdk.nashorn.api.scripting.NashornScriptEngine.eval(NashornScriptEngine.java:188)
at net.java.avatar.js.Server.eval(Server.java:312)
at net.java.avatar.js.Server.access$1000(Server.java:58)
at net.java.avatar.js.Server$SystemScriptRunner.run(Server.java:477)
at net.java.avatar.js.Server.runSystemScript(Server.java:172)
at net.java.avatar.js.Server.runEventLoop(Server.java:228)
at net.java.avatar.js.Server.runUserScripts(Server.java:213)
at net.java.avatar.js.Server.run(Server.java:152)
at net.java.avatar.js.Server.main(Server.java:104)