[PATCH 0/1] MR913: winegstreamer: Avoid accessing NULL pointer if transform didn't provide a sample.

[Rémi Bernon]

This can happen with asynchronous decoding, such as with the VA-API
decodebin plugin for H264.

This fixes the mf transform tests crashing when VA-API plugins are used.

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https://gitlab.winehq.org/wine/wine/-/merge_requests/913