Fix the tracking of nicks that were set just before nick reset (#4830)

Author: Jackenmen

redbot/cogs/mod/events.py

@@ -176,7 +176,7 @@ async def on_user_update(self, before: discord.User, after: discord.User):
 
     @commands.Cog.listener()
     async def on_member_update(self, before: discord.Member, after: discord.Member):
-        if before.nick != after.nick and after.nick is not None:
+        if before.nick != after.nick and before.nick is not None:
             guild = after.guild
             if (not guild) or await self.bot.cog_disabled_in_guild(self, guild):
                 return