Add DM AI disable check for Gurt

gurt/listeners.py

@@ -294,6 +294,11 @@ async def on_message_listener(cog: "GurtCog", message: discord.Message):
         and message.reference.resolved.author == cog.bot.user
     )
     gurt_in_message = "gurt" in message.content.lower()
+
+    if message.guild is None and (bot_mentioned or replied_to_bot or gurt_in_message):
+        await message.channel.send("AI functionality is disabled in DMs.")
+        return
+
     now = time.time()
     time_since_last_activity = now - cog.channel_activity.get(channel_id, 0)
     time_since_bot_spoke = now - cog.bot_last_spoke.get(channel_id, 0)