Refactor invite manager

src/cogs/invite_manager.py

@@ -1,6 +1,6 @@
 import discord
-from discord import app_commands
 from discord.ext import commands
+from typing import Optional
 
 from src.utils import Embeds, Error
 from src.config import Config
@@ -12,6 +12,9 @@ class Invite(commands.Cog):
   Handles welcoming new members
   """
 
+  client: commands.Bot
+
+
   def __init__(self, client: commands.Bot) -> None:
     self.client = client
 
@@ -24,9 +27,9 @@ async def on_ready(self):
   @commands.Cog.listener()
   async def on_member_join(self, member: discord.Member):
     guild = self.client.get_guild(Config.GUILD_ID)
-    welcome_channel = guild.get_channel(Config.WELCOME_CHANNEL_ID)
+    welcome_channel = guild and guild.get_channel(Config.WELCOME_CHANNEL_ID)
 
-    if welcome_channel:
+    if welcome_channel and isinstance(welcome_channel, discord.TextChannel):
       await welcome_channel.send(member.mention, embed = Embeds(
         title = member.global_name,
         description = f'**Welcome to the server!** 🎉\n\nDon\'t forget to `git checkout `<#{Config.RULE_CHANNEL_ID}>'