Cannot delete wiki containing backslash in the title on gitlab.com. E.g. "C\ style guide"

Summary

Cannot delete wiki containing backslash in the title on gitlab.com. E.g. "C\\ style guide" (double back slash). Url renders as: /wikis/C%5C-%5C---style-guide

Steps to reproduce

Create a wiki with with title "C\ style guide" and try to delete it

Example Project

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What is the current bug behavior?

wiki not deleted

What is the expected correct behavior?

wiki should be deleted

Relevant logs and/or screenshots

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Output of checks

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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

Expand for output related to the GitLab application check

(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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