Annoying Chromecast Popup

[mcattell]

I use my phone to play Spotify at work. Somebody in the office has a Chromecast running and often I get plagued by a stupid popup that gives me only two options - either to connect to the Chromecast now or later. Where is the "Dismiss" button. I shouldn't have to use the back button of my phone to get rid of it, since obviously I don't want to stream music through some random Chromecast that my colleague has set up.