avcodec/mjpegdec: Try to continue decoding on zero quant matrix value

A zero value in the quantization matrix is invalid but in practice will
just set the transform coefficient to zero after inverse quantization.
Try to continue decoding if the AV_EF_EXPLODE flag is not set.

Fixes ticket #9287.

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andriy Gelman <andriy.gelman@gmail.com>

libavcodec/mjpegdec.c

@@ -217,7 +217,9 @@ int ff_mjpeg_decode_dqt(MJpegDecodeContext *s)
         for (i = 0; i < 64; i++) {
             s->quant_matrixes[index][i] = get_bits(&s->gb, pr ? 16 : 8);
             if (s->quant_matrixes[index][i] == 0) {
-                av_log(s->avctx, AV_LOG_ERROR, "dqt: 0 quant value\n");
+                int log_level = s->avctx->err_recognition & AV_EF_EXPLODE ? AV_LOG_ERROR : AV_LOG_WARNING;
+                av_log(s->avctx, log_level, "dqt: 0 quant value\n");
+                if (s->avctx->err_recognition & AV_EF_EXPLODE)
                     return AVERROR_INVALIDDATA;
             }
         }