Trying to change the email of a subgroup in the Notifications settings results in 404

Summary

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Steps to reproduce

Example Project

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What is the current bug behavior?

You are redirected to a link like https://gitlab.com/profile/notifications/groups/GroupName%2FSubgroupName, which is a 404 page.

What is the expected correct behavior?

The email should get changed successfully.

Relevant logs and/or screenshots

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Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

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`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

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(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)


(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)


(we will only investigate if the tests are passing)

Possible fixes

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Edited by Iulian Onofrei