avcodec/nuv: rtjpeg with dimensions less than 16 would result in no decoded pixels thus reject it

Fixes: Timeout
Fixes: 6297/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_NUV_fuzzer-4882404863901696

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

libavcodec/nuv.c

@@ -199,6 +199,9 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
     case NUV_RTJPEG_IN_LZO:
     case NUV_RTJPEG:
         keyframe = !buf[2];
+        if (c->width < 16 || c->height < 16) {
+            return AVERROR_INVALIDDATA;
+        }
         break;
     case NUV_COPY_LAST:
         keyframe = 0;