Justin Bieber was unharmed after being grabbed by a stage invader at a Dubai concert today, though his piano came away worse for the wear. The star was at the piano playing "Believe" when a youth tackled him from behind, the Nation reports. Bieber's piano was overturned and left unplayable as security guards scuffled with the fan. The star managed to finish the song and returned for an encore after a short break. "Dubai," he later tweeted. "Nothing stops the show."