Minor edits

Author: jonchardy

src/App.tsx

@@ -121,7 +121,6 @@ class App extends React.Component<{}, AppState> {
    * @param obj a JSON-formatted string
    */
   public handleModelChange(obj: go.IncrementalData) {
-    if (obj === null) return;
     const insertedNodeKeys = obj.insertedNodeKeys;
     const modifiedNodeData = obj.modifiedNodeData;
     const removedNodeKeys = obj.removedNodeKeys;

src/components/Diagram.tsx

@@ -55,10 +55,10 @@ export class DiagramWrapper extends React.Component<DiagramProps, {}> {
   }
 
   /**
-   * Diagram initialization method, which is passed to the Diagram component.
+   * Diagram initialization method, which is passed to the ReactDiagram component.
    * This method is responsible for making the diagram and initializing the model, any templates,
    * and maybe doing other initialization tasks like customizing tools.
-   * The model's data should not be set here, as the Diagram component handles that.
+   * The model's data should not be set here, as the ReactDiagram component handles that.
    */
   private initDiagram(): go.Diagram {
     const $ = go.GraphObject.make;