Fix bug with missing commands

lib/rollbot/bot.py

@@ -57,7 +57,7 @@ class Rollbot(Generic[RawMsg]):
             return
 
         command_call = self.command_config.commands.get(command, None)
-        if command is None:
+        if command_call is None:
             await self.respond(Response.from_message(message, f"Sorry! I don't know the command {command}."))
             return