500 error message if clicking the "Upload" button when chaning a group avatar without having any image file selected for upload

[emilghittasv]

Preconditions
Sign in with an admin account.

Steps to reproduce
Steps to reproduce the behavior:

1. Go to https://support.allizom.org/en-US/groups/
2. Select a random group from the list.
3. Click on the "Change" button under the default group avatar.
4. Upload an image.
5. Click on the "Change" option under the newly uploaded image.
6. Click on the "Upload" button.

Expected behavior
Nothing happens since no files were selected via the file picker (or the Upload button is disabled in this case).

Actual behavior
500 error with FileNotFoundError

Screencasts

Desktop:

• OS: Windows 11
• Browser: Firefox

Additional context
Sentry fires https://mozilla.sentry.io/issues/6029282387/?project=4504326797197312&query=is%3Aunresolved%20issue.priority%3A%5Bhigh%2C%20medium%5D&referrer=issue-stream&statsPeriod=1h&stream_index=0

[emilghittasv]

Bug fix candidate for current sprint.