How to do recursion?

[JohnLCaron]

Im failing to do recursion:

    val group : Parser<OdlStruct> by (groupStart and zeroOrMore(group) and groupEnd).map {  // line 58
            (name1 : String, nested : List<OdlStruct>, name2 : String ) ->
        val result = OdlStruct(name1)
        result.nested.addAll(nested)
        result
    }

on input like:

GROUP=SwathStructure
    GROUP=SWATH_1
          GROUP=Dimension
          END_GROUP=Dimension
         ...
    END_GROUP=SWATH_1
END_GROUP=SwathStructure

I get error:

Caused by: java.lang.NullPointerException: Parameter specified as non-null is null: method com.github.h0tk3y.betterParse.grammar.Grammar.getValue, parameter <this>
	at com.github.h0tk3y.betterParse.grammar.Grammar.getValue(Grammar.kt)
	at com.sunya.netchdf.parser.OdlParser.getGroup(OdlParser.kt:58)
	at com.sunya.netchdf.parser.OdlParser.<clinit>(OdlParser.kt:58)

presumably from "zeroOrMore(group)"

I guess I need a to instantiate a new Parser instead of trying to reference the group(?), but im stymied how to do that.
Maybe something simple Im missing?

Thanks for your help and the cool library.