Ingest-convert.sh TypeError

I'm trying to convert filebeat-7.10.0-iis-error-pipeline to logstash config with
./ingest-convert.sh --input file:///root/error.json --output file:///root/iss-access.conf
I tried with java bundled with logstash 7.10.0 as well as "OpenJDK Runtime Environment (build 1.8.0_272-b10)"
I'm getting following error. Any ideas?

Warning: Nashorn engine is planned to be removed from a future JDK release
Exception in thread "main" javax.script.ScriptException: TypeError: Cannot read property "map" from undefined in <eval> at line number 78
        at jdk.scripting.nashorn/jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:477)
        at jdk.scripting.nashorn/jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:399)
        at jdk.scripting.nashorn/jdk.nashorn.api.scripting.NashornScriptEngine.invokeFunction(NashornScriptEngine.java:197)
        at org.logstash.ingest.JsUtil.convert(JsUtil.java:104)
        at org.logstash.ingest.Pipeline.main(Pipeline.java:35)
Caused by: <eval>:78 TypeError: Cannot read property "map" from undefined
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:57)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:213)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:185)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:172)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.Undefined.get(Undefined.java:161)
        at jdk.scripting.nashorn.scripts/jdk.nashorn.internal.scripts.Script$Recompilation$24$44AA$\^eval\_.ingest_pipeline_to_logstash(<eval>:78)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:659)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:513)
        at jdk.scripting.nashorn/jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:527)
        at jdk.scripting.nashorn/jdk.nashorn.api.scripting.ScriptObjectMirror.callMember(ScriptObjectMirror.java:202)
        at jdk.scripting.nashorn/jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:393)