Scrolling outside the PDF scroll area scrolls PDF

**Describe the bug**
When you scroll outside the PDF scroll area PDF is scrolled too

**To Reproduce**
Steps to reproduce the behavior:

**Expected behavior**
It should scroll page instead
**Desktop (please complete the following information):**
- OS: Ubuntu 24.04
- Browser [e.g. chrome, safari]: Chrome

Reproduce the issue in Chrome on Ubuntu 24.04 using the attached screenshot as context, then locate the PDF scroll area and the surrounding page scroll behavior. Done means scrolling outside the PDF area scrolls the page instead of the PDF.

索引モデルが issue の本文から書いたものです。