avcodec/exr: check tile_attr.x/ySize

Fixes: division by zero
Fixes: 473579863/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EXR_DEC_fuzzer-5105281257504768

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c5ccc13fe0)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/exr.c

@@ -2218,6 +2218,8 @@ static int decode_frame(AVCodecContext *avctx, void *data,
     }
 
     if (s->is_tile) {
+        if (s->tile_attr.ySize <= 0 || s->tile_attr.xSize <= 0)
+            return AVERROR_INVALIDDATA;
         nb_blocks = ((s->xdelta + s->tile_attr.xSize - 1) / s->tile_attr.xSize) *
         ((s->ydelta + s->tile_attr.ySize - 1) / s->tile_attr.ySize);
     } else { /* scanline */