Hook for empty message sent

I know there is a hook for a message being sent but I'm wondering if the server can detect when a player does not type anything and simply presses enter once again.

I understand if this is client-centric and can not be monitored by the server.

 

Making a help button that shows below the chat box only when you press enter to type and then hides when the chat box is no longer visible. Have it hooked to rebinding the return key to make a command console call while also doing chat.open.

 

Interesting find: If you half-press the enter key with the chatbox open it keeps the help button up. A full firm press on the return key closes the chatbox AND the help button as well...