Control Flow empty text field problem

I’ve updated my custom integration to use control flows (visonic alarm) and I have a problem with a string entry field.

I initially set the text to an empty string i.e “”
If the user sets the text string to something then it works OK
If the user wants to set it back to the empty string, deleting the content of the text entry does not work.

It looks like it works but returns the previous text entry.

I think this is a bug in the HA control flow but I’m not sure, please help