Changed message after "?setup", fixed a problem when deleting log_channel and main_category

Author: Taaku18

bot.py

@@ -147,7 +147,9 @@ def log_channel(self):
         channel_id = self.config.get('log_channel_id')
         if channel_id is not None:
             return self.get_channel(int(channel_id))
-        return self.main_category.channels[0]
+        if self.main_category is not None:
+            return self.main_category.channels[0]
+        return None
 
     @property
     def snippets(self):
@@ -463,6 +465,16 @@ async def on_guild_channel_delete(self, channel):
             return
 
         if not isinstance(channel, discord.TextChannel):
+            if self.config.get('main_category_id') == channel.id:
+                await self.config.update({
+                    'main_category_id': None
+                })
+            return
+
+        if self.config.get('log_channel_id') == channel.id:
+            await self.config.update({
+                'log_channel_id': None
+            })
             return
 
         thread = await self.threads.find(channel=channel)

cogs/modmail.py

@@ -27,7 +27,8 @@ async def setup(self, ctx):
         """Sets up a server for Modmail"""
         if self.bot.main_category:
             return await ctx.send(
-                f'{self.bot.modmail_guild} is already set up.')
+                f'{self.bot.modmail_guild} is already set up.'
+            )
 
         category = await self.bot.modmail_guild.create_category(
             name='Modmail',
@@ -40,15 +41,18 @@ async def setup(self, ctx):
             name='bot-logs', category=category
         )
 
-        await log_channel.edit(
-            topic='You can delete this channel '
-                  'if you set up your own log channel.'
+        embed = discord.Embed(
+            title='Friendly Reminder:',
+            description='You may use the `config set log_channel_id '
+                        '<channel-id>` command to set up a custom log channel'
+                        ', then you can delete the default '
+                        f'{log_channel.mention} channel.',
+            color=discord.Color.blurple()
         )
 
-        await log_channel.send(
-            'Use the `config set log_channel_id` '
-            'command to set up a custom log channel.'
-        )
+        embed.set_footer(text=f'Type "{self.bot.prefix}help" '
+                              'for a complete list of commands.')
+        await log_channel.send(embed=embed)
 
         self.bot.config['main_category_id'] = category.id
         self.bot.config['log_channel_id'] = log_channel.id

core/thread.py

@@ -491,13 +491,17 @@ async def _find_from_channel(self, channel):
         # BUG: When discord fails to create channel topic.
         # search through message history
         elif channel.topic is None:
-            async for message in channel.history(limit=100):
-                if message.embeds:
-                    embed = message.embeds[0]
-                    if embed.footer.text:
-                        user_id = match_user_id(embed.footer.text)
-                        if user_id != -1:
-                            break
+            try:
+                async for message in channel.history(limit=100):
+                    if message.embeds:
+                        embed = message.embeds[0]
+                        if embed.footer.text:
+                            user_id = match_user_id(embed.footer.text)
+                            if user_id != -1:
+                                break
+            except discord.NotFound:
+                # When the channel's deleted.
+                pass
 
         if user_id != -1:
             if user_id in self.cache: