I got a Black Spindle Saturday, but can't level it up. It dropped at 290 and I'm trying to level it up to 400. I have it on my character (not equipped) and unlocked. When I try to infuse another special weapon into it, I get an error that basically says "there are no weapons available for infusion" I have exotic shards, legendary marks and everything that I need to infuse, but it doesn't work. Are you not able to infuse this gun to a higher light level?