Small bug discovered in plugin

Hi there, I’ve discovered a bug in the plugin, or so it seems.
There’s a deprecation message triggered, on a php5.6 operated wordpress site, please view this screenshot:
https://prntscr.com/i8a5qk
Otherwise it still does what it was supposed to, so the links towards the mobile / full version still gets displayed, functionality still is ok, but it displays these warnings above every page.

Thanks