Fixed typos in throttling code.

IPython/html/static/notebook/js/widget.js

@@ -72,13 +72,12 define(["components/underscore/underscore-min",
                 // Send buffer if this message caused another message to be
                 // throttled.
                 if (this.msg_buffer != null &&
-                    this.msg_throttle == this.pending_msgs && 
-                    this.msg_buffer.length > 0) {
+                    this.msg_throttle == this.pending_msgs) {
                         
-                        var output_area = this._get_msg_output_area(msg);
+                    var output_area = this._get_output_area(msg.parent_header.msg_id);
                         var callbacks = this._make_callbacks(output_area);
                         var data = {sync_method: 'update', sync_data: this.msg_buffer};
-                        comm.send(data, callbacks);   
+                    this.comm.send(data, callbacks);   
                         this.msg_buffer = null;
                 } else {