avcodec/tiff: reset sampling[] if its invalid

Fixes divission by 0
Fixes: clusterfuzz-testcase-minimized-5592896440893440

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f08122fbe0)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/tiff.c

@@ -1018,6 +1018,7 @@ static int tiff_decode_tag(TiffContext *s, AVFrame *frame)
             s->subsampling[i] = ff_tget(&s->gb, type, s->le);
             if (s->subsampling[i] <= 0) {
                 av_log(s->avctx, AV_LOG_ERROR, "subsampling %d is invalid\n", s->subsampling[i]);
+                s->subsampling[i] = 1;
                 return AVERROR_INVALIDDATA;
             }
         }