fix(ticket): disallow empty message

[AugustinMauroy]

PR Checklist

• The PR title follows
  conventional commits
• Is this closing an open issue? If so, link it, else include a proper
  description of the changes and rason behind them.
• Does the PR have changes to the frontend? If so, include screenshots or a
  recording of the changes.
  
  If it affect colors, please include screenshots/recording in both
  light and dark mode.
• Does the PR have changes to the backend? If so, make sure tests are added.
  
  And if changing dababase queries, be sure you have ran sqlx prepare
  and committed the changes in the .sqlx directory.

[crowlKats]

LGTM, thanks