Cited Books button missing in Popup

[cgorringe]

Describe the bug The blue "Books" button is missing in the toolbar popup, while visiting a relevant Wikipedia page with its setting turned on.

To Reproduce Steps to reproduce the behavior:

1. Turn on "Wikipedia Resources" in Settings
2. Go to https://en.wikipedia.org/wiki/Vincent_van_Gogh
3. Scroll down to Sources. Notice that the Archive icons correctly display alongside ISBN numbers and that the books API is working correctly. (from inspecting background page, Network tab)
4. Click on toolbar icon to notice that "Papers" button displays, but "Books" is missing.

Expected behavior Expect the "Books" button to display, so that the user may click on it to open a Cited Books window.

Screenshots

Environment (please complete the following information):

• Webextension version: 3.4.1
• Browser + version: Chrome 126.0.6478.127
• OS + version: macOS 14.5

[cgorringe]

After trying it again, the blue "Books" button did show up in the popup for the Van Gogh page, so it appears to work correctly some of the time. I tested some more URLs.

These URLs didn't display the "Books" button:

• https://en.wikipedia.org/wiki/Paper
• https://en.m.wikipedia.org/wiki/Paper
• https://simple.wikipedia.org/wiki/Paper
• https://es.wikipedia.org/wiki/Papel

This displayed the "Books" button but not the embedded Archive icons:

• https://en.wikipedia.org/wiki/World_War_II

These URLs worked correctly:

• https://en.wikipedia.org/wiki/Barack_Obama
• https://en.wikipedia.org/wiki/Bob_Marley
• https://de.wikipedia.org/wiki/Papier