Null out threadContext->gba when shutting down
Null out threadContext->gba when shutting down

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