Fixed a bug causing players to see unrelated guilds' #ally channels

- The issue would only happen if the #ally channel is on auto-join, when
  a guild is first loaded.
- Follow-up to cd2f5e4a687b2abbdb9d795e5c91b874aa0d2546
- Special thanks to Ind.

Signed-off-by: Haru <haru@dotalux.com>