src/vs/workbench/browser/parts/editor/editorGroupView.ts/EditorGroupView/lock
class EditorGroupView:	lock(locked: boolean): void {
		if (this.accessor.groups.length === 1) {
			// Special case: if only 1 group is opened, never allow to lock
			// to ensure editors can always open in the "default" editor group
			locked = false;
		}

		this.model.lock(locked);
	}