Fix reply/mention notifications from muted users.

Consider the case of the current /notifications filter condition:
    WHERE ... NOT ((comments.sentto = 2) AND (users.is_muted))

SELECT 1 WHERE NOT ((null = 2) AND (true)); ⇒ 0 rows
SELECT 1 WHERE NOT ((1 = 2) AND (true)); ⇒ 1 row
SELECT 1 WHERE NOT ((2 = 2) AND (true)); ⇒ 0 rows

We want the first expression, where comments.sentto = null, to evaluate
to false, not to null, so it negates to true. Behavior as written is:

SELECT 1 WHERE NOT ((null = 2) AND (true)); →
SELECT 1 WHERE NOT (null AND true); →
SELECT 1 WHERE NOT null; →
SELECT 1 WHERE null;

Which guarantees a null return set. If we check first for non-nullity:

SELECT 1 WHERE NOT ((null IS NOT null) AND (null = 2) AND (true)); ⇒ 1
SELECT 1 WHERE NOT ((1 IS NOT null) AND (1 = 2) AND (true)); ⇒ 1
SELECT 1 WHERE NOT ((2 IS NOT null) AND (2 = 2) AND (true)); ⇒ 0

files/classes/user.py

@@ -591,7 +591,7 @@ class User(Base):
 					Notification.user_id == self.id,
 					Comment.is_banned == False,
 					Comment.deleted_utc == 0,
-					not_(and_(Comment.sentto == MODMAIL_ID, User.is_muted)),
+					not_(and_(Comment.sentto != None, Comment.sentto == MODMAIL_ID, User.is_muted)),
 				))
 		
 		if not self.can_see_shadowbanned:

files/routes/notifications.py

@@ -273,7 +273,7 @@ def notifications(v):
 		Comment.deleted_utc == 0,
 		Comment.body_html.notlike('%<p>New site mention%<a href="https://old.reddit.com/r/%'),
 		or_(Comment.sentto == None, Comment.sentto == MODMAIL_ID),
-		not_(and_(Comment.sentto == MODMAIL_ID, User.is_muted)),
+		not_(and_(Comment.sentto != None, Comment.sentto == MODMAIL_ID, User.is_muted)),
 	)
 
 	if v.admin_level < PERMS['USER_SHADOWBAN']: