Cannot switch subsites in the CMS when on the 'Settings' section of a page

[LeviWB]

Subsites version: 2.4.0
CMS version: 4.7.0
Browser: Chrome 89.0

Steps to replicate:

1. Setup a SilverStripe instance with a main site and one or more subsites.
2. Create and publish a page on the main site.
3. Navigate back to the page within the CMS and change to the 'Settings' tab.
4. Switch to a subsite using the subsite dropdown in the CMS navigation bar.

Expected: the CMS should switch to the 'Pages' view of the selected subsite

Actual: the CMS reloads the page already being viewed and remains on the 'Main site' rather than the selected subsite.

This bug also appears to occur if you're on the 'History' tab.

[GuySartorelli]

Fixed in #490. It will be tagged automatically when CI has finished running on the branch.

[GuySartorelli]

The fix needed to be reverted - see #538