Wordpress is encouraging me to update my PHP but I wanted to make sure the Hemma Theme can support PHP 7.2 or higher?
I haven't tested it yet but tTheme should support any 7.x PHP version, and maybe higher. In case of issues you can eventually switch back to a lower PHP version and report issues.
In any case, I'd recommend to update anything unless you have a really outdated PHP version, or you really need it (eg. a plugin that needs an update).
It's a plugin saying it's a potential security vulnerability but I feel like they always say that. PHP Compatibility Checker said the theme was compatible. Ok thanks!