If you are using  Online Store 2.0 theme. You can activate popup form app embed feature in your theme. When the app is uninstalled, the app embeds will be removed automatically.

1. From your Shopify admin, go to Online Store > Themes.
2. Find the theme that you want to edit, and then click Customize.
3. Click Theme   settings.
4. Click the App embeds tab.
5. Click the toggle to activate Enable Popup Form.
6. Save.