Tile corruption on sprite

Reproducible by watching Super Mario Land attract mode. 
The issue happens on the demo of world 3-3 
![sml sprite tile bug](https://user-images.githubusercontent.com/882269/46669210-12454b00-cbcf-11e8-9cef-f7e26f2b573a.gif)
Note the double flicker (only one visible in gif due to reduced frame rate) of scanline 0 just before the occurrence. Related?
