show nothing for siteInfo on about: pages

[diracdeltas]

fix #8299

Test Plan:

1. open example.com
2. open a new tab
3. show siteInfo on example.com, then use Cmd+2 to switch to the second tab
4. no siteInfo should show on the second tab

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

Test Plan:

[darkdh]

lgtm++