Fiddle Ult in a tower and get stuck

Hello Riot

I just played a Legend of the Poro King with Fiddlesticks (Spectral Skin). I managed to Ult inside the right Nexus tower (north side) and get stuck there. I just stayed in there until i got killed after 10 seconds or something. I have no Screenshot or anything because I missed to do one. Sorry for that.

Kind regards Dongu