Describe the bug

For modals with a long scrolling long content, if modal show/hide animation is disabled with no-fade prop, when modal is opened page scrolls to the top of the modal.

Steps to reproduce the bug

1. Go to https://bootstrap-vue.js.org/docs/components/modal#scrolling-long-content
2. Click on the button Launch overflowing modal. You can see that modal is opened as expected and there's a top margin on modal-dialog.
3. Now edit the example by double clicking the code block and add no-fade prop to <b-modal> component. Then click the launch modal button again.
4. You can see that page is scrolled to the top of the modal.

Expected behavior

Should work the same when animations are enabled.

Versions

Libraries:

• BootstrapVue: 2.0.0-rc.28
• Bootstrap: 4.3.1
• Vue: 2.6.10

Environment:

• OS: Windows 10
• Browser: Chrome
• Version: 76.0.3809.132 (Official Build) (64-bit)

Demo link

Reproducible at https://bootstrap-vue.js.org/docs/components/modal#scrolling-long-content

Additional context

N/A