Fix API error handling in siac
Fix API error handling in siac

The response body was being decoded after it was closed in the event of
an error. Thanks @droghio for finding this!

rivine/rivine,mharkus/Sia,mnsl/Sia,MrStrong/Sia,NebulousLabs/Sia,mtlynch/Sia,ericflo/Sia,ericflo/Sia,mharkus/Sia,MrStrong/Sia,rivine/rivine,ChrisSchinnerl/Sia,mtlynch/Sia,NebulousLabs/Sia,mnsl/Sia,ChrisSchinnerl/Sia