There's a space joining "Login or subscribe text (displayed if not logged in)" and "Suggestion text for plans subscription (always displayed)". So if you empty both of those parameters a space is still sent to enqueueMessage and it'll output. To fix empty spaces from adding to the message queue at all please make the below change.
IN: libraries/CBLib/CB/Legacy/CBframework.php
ON: Line 543
FROM:
TO:
Code:
if ( trim( $message ) != '' ) {
Now empty both parameters and no more message.