Typing "[" or ";" in the server address grays out certain buttons

When typing "[" or ";" in the server address bar the "Join Server" button for direct connection and "Done" button in add server stay greyed out

Reproduce

1. Open 21w14a.

2. Go into the Multiplayer Menu.
3. Click on Direct Connection.
4. Type "[".
5. The "Join Server" button is grayed out.