Help needed with LrDialogs.showBezel

Hi all.

I need a bit of help with LrDialogs.showBezel

Here the example code (this is super basic code but it helps to illustrate a potential use case)

local LrDevelopController = import "LrDevelopController"

    local maskId = LrDevelopController.getSelectedMask ()
     LrDevelopController.deleteMask (maskId)

So I know how to use  LrDialogs.showBezel (message) already but I don't know how to make it appear specifically in some cases and not all the time.

Using the example code I would like to make a bezel to appear OLY if there is no mask selected.

Tis probably a super simple thing to do, so forgive my stupidity, but this is escaping me.

.