fix bad editor flashing on startup

src/vs/workbench/electron-browser/workbench.ts

@@ -825,7 +825,7 @@ export class Workbench implements IPartService {
 	private createEditorPart(): void {
 		const editorContainer = $(this.workbench)
 			.div({
-				'class': ['part', 'editor', 'monaco-editor-background'],
+				'class': ['part', 'editor', 'monaco-editor-background', 'empty'],
 				id: Identifiers.EDITOR_PART,
 				role: 'main'
 			});