GUI: Fix file select indexing
GUI: Fix file select indexing

libretro/mgba,askotx/mgba,Iniquitatis/mgba,Anty-Lemon/mgba,sergiobenrocha2/mgba,jeremyherbert/mgba,Iniquitatis/mgba,sergiobenrocha2/mgba,Anty-Lemon/mgba,jeremyherbert/mgba,iracigt/mgba,libretro/mgba,Anty-Lemon/mgba,MerryMage/mgba,Touched/mgba,cassos/mgba,MerryMage/mgba,mgba-emu/mgba,askotx/mgba,sergiobenrocha2/mgba,iracigt/mgba,askotx/mgba,mgba-emu/mgba,MerryMage/mgba,sergiobenrocha2/mgba,jeremyherbert/mgba,iracigt/mgba,sergiobenrocha2/mgba,askotx/mgba,mgba-emu/mgba,fr500/mgba,libretro/mgba,Touched/mgba,cassos/mgba,Iniquitatis/mgba,iracigt/mgba,Iniquitatis/mgba,mgba-emu/mgba,Touched/mgba,cassos/mgba,jeremyherbert/mgba,AdmiralCurtiss/mgba,libretro/mgba,fr500/mgba,fr500/mgba,AdmiralCurtiss/mgba,Anty-Lemon/mgba,fr500/mgba,AdmiralCurtiss/mgba,libretro/mgba