diff --git a/node_modules/ace_tree/lib/ace_tree/layer/heading.js b/node_modules/ace_tree/lib/ace_tree/layer/heading.js
index d0a0f66c..834155fd 100644
--- a/node_modules/ace_tree/lib/ace_tree/layer/heading.js
+++ b/node_modules/ace_tree/lib/ace_tree/layer/heading.js
@@ -58,7 +58,7 @@ function ColumnHeader(parentEl, renderer) {
             if (col.value && !col.getText)
                 col.getText = getColumnText;
             var w = col.width;
-            if (w.slice(-1) == "%") {
+            if (typeof w == "string" && w.slice(-1) == "%") {
                 col.flex = parseInt(w, 10) / 100;
                 col.$width = col.width;
             } else {
@@ -69,6 +69,7 @@ function ColumnHeader(parentEl, renderer) {
             col.pixelWidth = 0;
         }, this);
         columns.$fixedWidth = fixedWidth + "px";
+        columns.width = null;
         provider.columns = columns;
     };
     
diff --git a/node_modules/ace_tree/lib/ace_tree/list_data.js b/node_modules/ace_tree/lib/ace_tree/list_data.js
index 34895b72..6f9b45c0 100644
--- a/node_modules/ace_tree/lib/ace_tree/list_data.js
+++ b/node_modules/ace_tree/lib/ace_tree/list_data.js
@@ -14,8 +14,8 @@ oop.inherits(ListData, DataProvider);
 (function() {
     
     this.setRoot = function(array) {
-      this.visibleItems = array
-      this._signal("change");
+       this.visibleItems = array || [];
+       this._signal("change");
     };
     
     this.getDataRange = function(rows, columns, callback) {