avcodec/speedhq: Check width

Fixes: out of array access
Fixes: 50014/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SPEEDHQ_fuzzer-4748914632294400

Alternatively the buffer size can be increased

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/speedhq.c

@@ -498,7 +498,7 @@ static int speedhq_decode_frame(AVCodecContext *avctx, AVFrame *frame,
     uint32_t second_field_offset;
     int ret;
 
-    if (buf_size < 4 || avctx->width < 8)
+    if (buf_size < 4 || avctx->width < 8 || avctx->width % 8 != 0)
         return AVERROR_INVALIDDATA;
 
     quality = buf[0];