Merge pull request #1754 from afshin/mimetype-bugfix

Only update notebook mime type if information is available.

src/notebook/widget.ts

@@ -468,6 +468,9 @@ class StaticNotebook extends Widget {
    */
   private _updateMimetype(): void {
     let info = this._model.metadata.get('language_info') as nbformat.ILanguageInfoMetadata;
+    if (!info) {
+      return;
+    }
     this._mimetype = this._mimetypeService.getMimeTypeByLanguage(info);
     each(this.widgets, widget => {
       if (widget.model.type === 'code') {

tutorial/notebook.md

@@ -87,7 +87,7 @@ also contains an [OutputAreaWidget](http://jupyterlab.github.io/jupyterlab/class
 An OutputAreaWidget is responsible for rendering the outputs in the
 [OutputAreaModel](http://jupyterlab.github.io/jupyterlab/classes/_outputarea_model_.outputareamodel.html)
 list. An OutputAreaWidget uses a
-notebook-specific [RenderMime](http://jupyterlab.github.io/jupyterlab/classes/_rendermime_index_.rendermime.html)
+notebook-specific [RenderMime](http://jupyterlab.github.io/jupyterlab/classes/_rendermime_rendermime_.rendermime.html)
 object to render `display_data` output messages.
 
 #### Rendering output messages