Switching groups when viewing a diff leads to error about missing v1 param in url

[davidscotson]

When viewing an ouwiki history diff in a wiki per group setup with a url like:

mod/ouwiki/diff.php?id=1248&group=77&v2=15&v1=13

You can see the group selector dropdown on the page and using it will take you to a url like:

mod/ouwiki/diff.php?id=1248&group=76

which corretly changes the group id but loses the rest of the url and present you with the error message:

A required parameter (v1) was missing

One solution would be to not show the group selector on this page. Since the group wikis are seperate and have seperate edit histories it doesn't really make sense to switch to the same diff in a different group's wiki.

Originally spotted in a moodle 4.5 site we were testing for upgrade, with plugin version 2024020100 but I can replicate the issue on a moodle 4.1 site too, with version 2022092300