"Back to top" button bug

[Zen-44]

Describe the bug
The Back to top button when scrolling in the oracle section doesn't display properly

Module
Pick one of:

• Oracle voting

To Reproduce
Steps to reproduce the behavior:

1. Go to the oracle section
2. Scroll down on the All tab (or any tab with sufficient content allowing scrolling)
3. See the Back to top button appear briefly and disappear if you continue scrolling

Expected behavior
The Back to top button should appear and remain there if continuing to scroll down

Identity context

• N/A

Idena Client logs
N/A

Screenshots / Screencasts
N/A

Environment:

• OS: Windows 10
• Node mode: VPS
• Client version 0.34.1
• Node version 0.30.3

Additional info
The issue is present on the web app as well.