lang: core, funcs: Use the correct zero type

I wasn't using the correct contained type here.

lang/core/list/list_lookup_func.go

@@ -232,7 +232,7 @@ func (obj *ListLookupFunc) Copy() interfaces.Func {
 func (obj *ListLookupFunc) Function(ctx context.Context, input []types.Value) (types.Value, error) {
 	l := (input[0]).(*types.ListValue)
 	index := input[1].Int()
-	//zero := l.Type().New() // the zero value
+	//zero := l.Type().Val.New() // the zero value
 
 	// TODO: should we handle overflow by returning zero?
 	if index > math.MaxInt { // max int size varies by arch

lang/core/map/map_lookup_func.go

@@ -234,7 +234,7 @@ func (obj *MapLookupFunc) Copy() interfaces.Func {
 func (obj *MapLookupFunc) Function(ctx context.Context, input []types.Value) (types.Value, error) {
 	m := (input[0]).(*types.MapValue)
 	key := input[1]
-	//zero := m.Type().New() // the zero value
+	//zero := m.Type().Val.New() // the zero value
 
 	val, exists := m.Lookup(key)
 	if exists {

lang/funcs/list_lookup_func.go

@@ -186,7 +186,7 @@ func (obj *ListLookupFunc) Stream(ctx context.Context) error {
 
 			l := (input.Struct()[listLookupArgNameList]).(*types.ListValue)
 			index := input.Struct()[listLookupArgNameIndex].Int()
-			zero := l.Type().New() // the zero value
+			zero := l.Type().Val.New() // the zero value
 
 			// TODO: should we handle overflow by returning zero?
 			if index > math.MaxInt { // max int size varies by arch

lang/funcs/map_lookup_func.go

@@ -189,7 +189,7 @@ func (obj *MapLookupFunc) Stream(ctx context.Context) error {
 
 			m := (input.Struct()[mapLookupArgNameMap]).(*types.MapValue)
 			key := input.Struct()[mapLookupArgNameKey]
-			zero := m.Type().New() // the zero value
+			zero := m.Type().Val.New() // the zero value
 
 			var result types.Value
 			val, exists := m.Lookup(key)