Fix a real bug, exposed by my recent change to the rts_evalIO() API.  Yay!
Fix a real bug, exposed by my recent change to the rts_evalIO() API.  Yay!

ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix