Marshmello Sued by Arty for Ripping Off One Republic's 'I Lived' Remix

Marshmello's mega hit "Happier" has another artist PISSED ... claiming in a new lawsuit the famous DJ jacked his remix. Artem Stoliarov -- aka Arty -- is suing Marshmello claiming the DJ's track "Happier" is almost identical to Arty's remix of One…