Fix moderation alerts being sent for boards

When a user is subscribed to both, a topic and the board the topic belongs to and the topic has a moderation action then it would also issue a duplicate (but empty) alert for the board as well

Signed-off-by: Shitiz Garg <mail@dragooon.net>
Merge pull request #2449 from Dragooon/release-2.1

Fix moderation alerts being sent for boards
meh... I forgot we are referencing files and folders
not vars! #2451

Signed-off-by: Suki <suki@missallsunday.com>
Merge pull request #2452 from MissAllSunday/writable_files

meh... I forgot we are referencing files and folders
Merge branch 'release-2.1' of git://github.com/simplemachines/SMF2.1 into release-2.1

# By Shitiz Garg (1) and Suki (1)
# Via Jessica González (1) and others
* 'release-2.1' of git://github.com/simplemachines/SMF2.1:
  meh... I forgot we are referencing files and folders not vars! #2451
  Fix moderation alerts being sent for boards