Comment detail: fix crash when replying to a comment

[ScoutHarris]

Fixes #n/a

This fixes a crash when replying to a comment from comment details.

To test:

• Go to Comments.
• Select a Comment.
• Enter a reply and send.
• Verify the app doesn't crash.
• Return to the Comments list.
• Verify your reply appears in the Comments list.

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[aerych]

Hola @ScoutHarris 👋
Looks good to me! Tested as described. There was no crash, and the new reply appeared in the list.
!