Fix crash for some homebrew games (Another World, T2002, maybe some retail too?) using a sprite scaling method in Mode 4

These two games crash at the intro right as it tries to scale. Patch courtesy of VBA-M upstream: http://sourceforge.net/p/vbam/code/HEAD/tree/trunk/src/gba/GBAGfx.h#l548 Note: need to rebase off of VBA-M soon.