homer script, fix repeated response to robot hearing a specific string

When the robot responds after hearing the message `beer`, it generates a message string to the chat window with `beer` in the message also. Because it detects the word `beer`, it will respond again with the string and keep on repeating because it hears the word `beer` repeatedly.

I added a check to see if it's a regular user that is providing the command/key or if it's the robot so as to avoid the repetition.