handUp arrow (div) is clickable from any height on page

[eharkins]

Current Behavior
The narratives up arrow is clickable from any height on the page, and covers other links up in certain areas.

Expected behavior
The up arrow should only be clickable when hovering over its icon.

How to reproduce
Steps to reproduce the current behavior:

1. Go to http://nextstrain.org/narratives/ncov/sit-rep/2020-04-10?n=1
2. Hover over the up arrow and trace your mouse down, keeping it in the same place in the lateral dimension, so that the mouse keeps showing the link style cursor hand.
3. You can click anywhere on the page within the lateral bounds of the up arrow (excluding clicking on the down arrow since it is inserted into the DOM on the same z-axis but after the up arrow - I think this is how it works) and it will go to the previous page.

Possible solution
Add an explicit CSS heigh to the up arrow div (and thereby the down arrow div too since they are created programmatically with the same function).

Your environment: if browsing Nextstrain online

• Operating system: macOS High Sierra 10.13.4
• Browser: Chrome 80.0.3987.149 (Official Build) (64-bit)

Additional context