Merge branch 'master' into doc/api

lib/ace/layer/text.js

@@ -132,6 +132,11 @@ var Text = function(parentEl) {
             }
 
         }
+        
+        // Size and width can be null if the editor is not visible or
+        // detached from the document
+        if (!this.element.offsetWidth)
+            return null;
 
         var style = this.$measureNode.style;
         var computedStyle = dom.computedStyle(this.element);