av_log callback called with bad parameters (NULL AVClass)

[mibby]

RE: ​https://github.com/shinchiro/mpv-winbuild-cmake/issues/728

[ffmpeg] av_log callback called with bad parameters (NULL AVClass).
[ffmpeg] This is a bug in one of FFmpeg libraries used.
Using hardware decoding (d3d12va-copy).

Warning is caused by incorrect av_log usage by the d3d12 context code in ffmpeg.

diff --git a/libavutil/hwcontext_d3d12va.c b/libavutil/hwcontext_d3d12va.c
index 6507cf69c15e..339572679001 100644
--- a/libavutil/hwcontext_d3d12va.c
+++ b/libavutil/hwcontext_d3d12va.c
@@ -660,7 +660,7 @@ static int d3d12va_device_create(AVHWDeviceContext *hwdev, const char *device,
             DXGI_ADAPTER_DESC desc;
             hr = IDXGIAdapter2_GetDesc(pAdapter, &desc);
             if (!FAILED(hr)) {
-                av_log(ctx, AV_LOG_INFO, "Using device %04x:%04x (%ls).\n",
+                av_log(hwdev, AV_LOG_INFO, "Using device %04x:%04x (%ls).\n",
                        desc.VendorId, desc.DeviceId, desc.Description);
             }
         }
@@ -668,7 +668,7 @@ static int d3d12va_device_create(AVHWDeviceContext *hwdev, const char *device,
         hr = priv->create_device((IUnknown *)pAdapter, D3D_FEATURE_LEVEL_12_0, &IID_ID3D12Device, (void **)&ctx->device);
         D3D12_OBJECT_RELEASE(pAdapter);
         if (FAILED(hr)) {
-            av_log(ctx, AV_LOG_ERROR, "Failed to create Direct 3D 12 device (%lx)\n", (long)hr);
+            av_log(hwdev, AV_LOG_ERROR, "Failed to create Direct 3D 12 device (%lx)\n", (long)hr);
             return AVERROR_UNKNOWN;
         }
     }