Icons missing in the supersidebar on oauth pages

Summary

When connecting apps or using the "log in with GitLab" feature, you're taken to an authorization screen. On this screen, none of the navigation icons load correctly.

Steps to reproduce

1. Make sure the new navigation is enabled on GitLab.com.
2. Go to https://forum.gitlab.com/login
3. Click on "with GitLab"
4. You should be taken to the oauth page. If not, revoke your access and start again.

To revoke access to forum.gitlab.com.

1. Go to https://gitlab.com/-/profile/applications
2. Scroll down to the "Authorized Applications" table
3. Click "Revoke" next to forum.gitlab.com

This works for any application that uses GitLab Oauth.

What is the current bug behavior?

Everything loads fine, but all the icons are missing on the page.

What is the expected correct behavior?

The icons should be there.

Relevant logs and/or screenshots

Possible fixes

I'm not sure what's causing the issue, but it's not the new navigation per-se. All the icons that are in Vue applications fail to load. This wasn't apparent with the old navigation as this was rendered in HAML.

It seems the SVG path is missing from all the Vue-rendered SVGs. The file is there, but the reference if off.

<svg data-testid="profile-icon" role="img" aria-hidden="true" class="gl-ml-2 item-icon gl-icon s16">
  <use href="undefined#profile"></use>
</svg>