Segfault when trying to enter fullscreen.

On latest git, with Glide64 Retroarch crashes when I try to enter fullscreen. (not game specific)

RetroArch [WARN] :: init_controllers :: Input device ID 517 is unknown to this libretro implementation. Using RETRO_DEVICE_JOYPAD.
RetroArch [WARN] :: init_controllers :: Input device ID 517 is unknown to this libretro implementation. Using RETRO_DEVICE_JOYPAD.
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: ROM Database: /home/user/.ra/system/mupen64plus.ini
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Unable to open rom database file '/home/e/.ra/system/mupen64plus.ini'.
RetroArch: rarch_log_libretro: [libretro INFO] :: EmuThread: M64CMD_ROM_OPEN
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Goodname: SUPER MARIO 64 (unknown rom)
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Headername: SUPER MARIO 64
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Name: SUPER MARIO 64      
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: MD5: 20B854B239203BAF6C961B850A4A51A2
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: CRC: 635a2bff 8b022326
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Imagetype: .v64 (byteswapped)
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Rom size: 8388608 bytes (or 8 Mb or 64 Megabits)
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: ClockRate = f
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Version: 1444
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Manufacturer: Nintendo
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Cartridge_ID: 4d53
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Country: USA
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: PC = 80246000
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Save type: 5
RetroArch: rarch_log_libretro: [libretro INFO] :: EmuThread: M64CMD_ROM_GET_HEADER
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: ConfigGetParamBool(): Parameter 'Fullscreen' not found!
ReadSpecialSettings: DEFAULT
Convoluted Cosine resampler (SSE) - precision = 1 : CC_upsample @1.000000 
RetroArch: rarch_log_libretro: [libretro INFO] :: EmuThread: M64CMD_EXECUTE. 
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Memory initialized
ReadSpecialSettings: DEFAULT
ReadSpecialSettings: SUPER MARIO 64
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: ConfigGetParamBool(): Parameter 'Fullscreen' not found!
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: Starting R4300 emulator: Dynamic Recompiler
RetroArch: rarch_log_libretro: [libretro INFO] :: Glide64 ucode = 3a1cbac3
RetroArch: rarch_log_libretro: [libretro INFO] :: Microcode 0 - RSP SW 2.0X (Super Mario 64)
RetroArch: rarch_log_libretro: [libretro INFO] :: microcheck: old ucode: 2,  new ucode: 0
RetroArch: rarch_log_libretro: [libretro INFO] :: mupen64plus: ConfigGetParamBool(): Parameter 'Fullscreen' not found!
RetroArch: rarch_log_libretro: [libretro INFO] :: Glide64 ucode = 3a1cbac3
RetroArch: rarch_log_libretro: [libretro INFO] :: Microcode 0 - RSP SW 2.0X (Super Mario 64)
RetroArch: rarch_log_libretro: [libretro INFO] :: microcheck: old ucode: 0,  new ucode: 0
Segmentation fault

I tried to figure it out myself, sorry.

Reproduce the crash with the Glide64 renderer and fullscreen transition using the reported Super Mario 64 case, then capture a debugger backtrace at the segmentation fault. Review the fullscreen-related path reached after the logged Glide64 initialization and confirm that entering fullscreen no longer crashes.