Describe the bug

In upload_modal.js has an extra comma that produces invalid HTML:
<img src="data:,", role="presentation" />

W3C HTML validator reports errors:

• Attribute "," not allowed on element "img"
• An img element must have an alt attribute

This causes the "passes HTML validation" test in accessibility_examples.rb to fail.

To Reproduce

1. Go to account page
2. Open avatar upload modal
3. Validate HTML with W3C validator

Expected behavior

Valid HTML without extra comma:
<img src="data:," role="presentation" />

Screenshots

No response

Stacktrace

No response

Extra data

• Device:
• Device OS:
• Browser:
• Decidim Version: 0.31.0
• Decidim installation:

Additional context

No response