WIP: Fix an error when user without Avatar icon comments on a design

What does this MR do?

Previously, after a user without a set avatar (in the user profile) commented on the design, this design could not be loaded again due to GraphQL error. This MR fixed the bug so discussions are loaded normally.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Related issue: #34512 (closed)