Comment # 3 on bug 1202828 from Marcus R���ckert

```
vainfo 
libva info: VA-API version 1.15.0
libva info: User environment variable requested driver 'vdpau'
libva info: Trying to open /usr/lib64/dri/vdpau_drv_video.so
libva info: Found init function __vaDriverInit_1_14
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.15 (libva 2.15.0)
vainfo: Driver version: Splitted-Desktop Systems VDPAU backend for VA-API -
0.7.4
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple            :    VAEntrypointVLD
      VAProfileMPEG2Main              :    VAEntrypointVLD
      VAProfileMPEG4Simple            :    VAEntrypointVLD
      VAProfileMPEG4AdvancedSimple    :    VAEntrypointVLD
      <unknown profile>               :    VAEntrypointVLD
      VAProfileH264Main               :    VAEntrypointVLD
      VAProfileH264High               :    VAEntrypointVLD
      VAProfileVC1Simple              :    VAEntrypointVLD
      VAProfileVC1Main                :    VAEntrypointVLD
      VAProfileVC1Advanced            :    VAEntrypointVLD
```

515.65.01 for a NVIDIA Corporation TU104 [GeForce RTX 2070 SUPER] (rev a1)

I just found the crash because i wanted to check another crash with coredumpctl
and then saw that FF crashed. then retried jitsi and saw that it is
reproducible.

one interesting thing i noticed in the stack trace: all the way up to
va_openDriver the dpy structure has a correct value. and the CTX()
macro/function does something weird and then the x11_dpy pointer is NULL.