Clicking the search box for filter files breaks the page when navigating from commit page. (BBCDEV-10633)

Summary

Page breaks when clicking "View source" from the commits' page then clicking the "Filter files".
Noticed that this only happens when the committed file(s) has a sub-folder.

This is specific to the flow of navigating to the source page from a specific commit. When navigating through this flow, no default source is selected/passed to the source browser.

See attached files.

Steps to reproduce:

1. Pushed a commit in your repository with a sub-folder.
2. Go to the commits page and find the specific commit hash
3. Click the "View source" button on the right side
4. Click "Filter files" text search on top.

Expected Results

The page should filter and search.

Actual Results

The page breaks with console errors.

Workaround

Choose Master from the reference dropdown, or any other branch/tag. You will then be able to use the search box as normal.

Alternatively, you can go directly to the source page for the specified repo, and by default master will be selected from the filter list. You can then use the search box as normal.