markdown tab not appears in comment creation

[lakostin]

• Gitea version (or commit ref):
  1.12.0+dev-268-g505e456f2
• Git version:
  2.17.1
• Operating system:
  Ubuntu 18.04.3 LTS
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Not relevant
• Log gist:

Description

Markdown tab not appears in comment creation. It only appears when editing the comment.

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Screenshots