Update cog.py

Author: plun1331

discord/cog.py

@@ -583,6 +583,11 @@ def remove_cog(self, name: str) -> Optional[Cog]:
         cog = self.__cogs.pop(name, None)
         if cog is None:
             return
+        
+        if hasattr(self, "_help_command"):
+            help_command = self._help_command
+            if help_command and help_command.cog is cog:
+                help_command.cog = None
 
         cog._eject(self)