에러 페이지, 모달, 누라된 메세지 추가

[kyungrae]

Description and Motivation

서버에서 누락된 메세지 추가, 채널 모달 생성시 발생하는 버그 해결, 에러페이지 렌더링 버그 해결

Types of changes

• [ ] Docs change
• [ ] dependency upgrade
• [ ] refactoring
• [x] Bug fix
• [ ] New feature
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Review

Checklist

• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.