It might be my mistake - I'll check it out and throw in a quick fix for the next version. In the meanwhile, I am sorry for the inconvenience - you might try to re-load an autosave and not pick the sword, though. Thank you for reporting!
After choosing to fight the gang at the top of the stairs, I looted their bodies. One of them had a shortsword which I picked up but could not move from the inventory slot nor sell; I believe it was from the gang's leader. Its text description would indicate it's a regular shortsword. Did I miss something that would enable me to get rid of it?