avcodec/utils: Check AVFrame width/height in avcodec_encode_video2()

This is similar to the format check
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/utils.c

@@ -2090,6 +2090,8 @@ int attribute_align_arg avcodec_encode_video2(AVCodecContext *avctx,
 
     if (frame && frame->format == AV_PIX_FMT_NONE)
         av_log(avctx, AV_LOG_WARNING, "AVFrame.format is not set\n");
+    if (frame && (frame->width == 0 || frame->height == 0))
+        av_log(avctx, AV_LOG_WARNING, "AVFrame.width or height is not set\n");
 
     av_assert0(avctx->codec->encode2);