fix typo

node_modules/ace/lib/ace/layer/font_metrics.js

@@ -172,7 +172,7 @@ var FontMetrics = exports.FontMetrics = function(parentEl, interval) {
     this.getCharacterWidth = function(ch) {
         var w = this.charSizes[ch];
         if (w === undefined) {
-            this.charSizes[ch] = this.$measureCharWidth(ch) / this.$characterSize.width;
+            w = this.charSizes[ch] = this.$measureCharWidth(ch) / this.$characterSize.width;
         }
         return w;
     };