diff --git a/src/tree-grid-directive.js b/src/tree-grid-directive.js index 08d514b..d3da0f8 100644 --- a/src/tree-grid-directive.js +++ b/src/tree-grid-directive.js @@ -252,7 +252,7 @@ } var key = function (x) { - return (x[col.field] === null ? "" : x[col.field].toLowerCase()); + return ((x[col.field] === null || x[col.field] === undefined) ? "" : x[col.field].toLowerCase()); }; switch (col.sortingType) {