avcodec/msvideo1: Check for too small dimensions

Such low resolution would result in empty output as a minimum of 4x4 is needed
We could also check for multiple of 4 dimensions but that is not needed

Fixes: Timeout
Fixes: 11191/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSVIDEO1_fuzzer-5739529588178944

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

libavcodec/msvideo1.c

@@ -62,6 +62,9 @@ static av_cold int msvideo1_decode_init(AVCodecContext *avctx)
 
     s->avctx = avctx;
 
+    if (avctx->width < 4 || avctx->height < 4)
+        return AVERROR_INVALIDDATA;
+
     /* figure out the colorspace based on the presence of a palette */
     if (s->avctx->bits_per_coded_sample == 8) {
         s->mode_8bit = 1;