Fix JSONEditor bug with undefined value (#379)

src/Explorer/Controls/JsonEditor/JsonEditorComponent.ts

@@ -59,11 +59,13 @@ export class JsonEditorViewModel extends WaitsForTemplateViewModel {
     this.params = params;
 
     this.params.content.subscribe((newValue: string) => {
+      if (newValue) {
         if (!!this.editor) {
           this.editor.getModel().setValue(newValue);
         } else {
           this.createEditor(newValue, this.configureEditor.bind(this));
         }
+      }
     });
 
     const onObserve: MutationCallback = (mutations: MutationRecord[], observer: MutationObserver): void => {