Minimum video length with MKV muxer?

[eumagga0x2a]

I thought, maybe I've cancelled a previous transcoding run, so that something might not have been cleaned up correctly and it influences the next run. However, I've reproduced this situation too, but to no avail.

Even if you canceled an encoding, the destructor and thus x264_encoder_close(x264_t *handle) was called. We don't care about initializing x264_picture_t pic_out, however. Unsure whether this can have such an effect, but maybe worth a precautionary correction as ffmpeg is doing it.