Don't use title exports in non v7 store

examples/cra-ts-kitchen-sink/src/stories/1-Button.stories.tsx

@@ -2,7 +2,9 @@ import React from 'react';
 import { action } from '@storybook/addon-actions';
 import { Button } from './Button';
 
+console.log('HERE');
 export default {
+  title: 'Button',
   component: Button,
 };
 

lib/client-api/src/ClientApi.ts

@@ -404,7 +404,9 @@ Read more here: https://github.com/storybookjs/storybook/blob/master/MIGRATION.m
     const { id: componentId, title } = defaultExport || {};
     if (!title) {
       throw new Error(
-        `Unexpected default export without title: ${JSON.stringify(fileExports.default)}`
+        `Unexpected default export without title in '${fileName}': ${JSON.stringify(
+          fileExports.default
+        )}`
       );
     }