Anchor links: headlines hidden behind toolbar

[mejo-]

Describe the bug
When opening an anchor link, the linked headline is hidden behind the toolbar.

To Reproduce
Steps to reproduce the behavior:

1. Create a Text document with page anchors
2. Click on a page anchor
3. See the linked headline being hidden behind the toolbar

Expected behavior
The linked headline should be visible.

Screenshots

@susnux maybe you could have a look since you implemented the anchor link feature (thanks again for that, btw) 😊