Revert "open editors: focus active group even if it does not have an editor"

This reverts commit 0e3a2219.

src/vs/workbench/parts/files/electron-browser/views/openEditorsView.ts

@@ -389,7 +389,7 @@ export class OpenEditorsView extends ViewletPanel {
 	}
 
 	private focusActiveEditor(): void {
-		if (this.editorGroupService.activeGroup) {
+		if (this.editorGroupService.activeGroup && this.editorGroupService.activeGroup.activeEditor /* could be empty */) {
 			const index = this.getIndex(this.editorGroupService.activeGroup, this.editorGroupService.activeGroup.activeEditor);
 			this.list.setFocus([index]);
 			this.list.setSelection([index]);