Qt: Fix building without OpenGL
Qt: Fix building without OpenGL

Iniquitatis/mgba,Anty-Lemon/mgba,Anty-Lemon/mgba,libretro/mgba,Iniquitatis/mgba,Anty-Lemon/mgba,libretro/mgba,Anty-Lemon/mgba,mgba-emu/mgba,libretro/mgba,libretro/mgba,libretro/mgba,Iniquitatis/mgba,mgba-emu/mgba,mgba-emu/mgba,mgba-emu/mgba,Iniquitatis/mgba