avformat/matroskadec: Fix infinite loop with bz decompression

The same check is added to zlib too, it seems not needed there though

Fixes: Infinite loop
Fixes: 43932/clusterfuzz-testcase-minimized-ffmpeg_dem_MATROSKA_fuzzer-6175167573786624

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/matroskadec.c

@@ -1709,7 +1709,7 @@ static int matroska_decode_buffer(uint8_t **buf, int *buf_size,
     case MATROSKA_TRACK_ENCODING_COMP_ZLIB:
     {
         z_stream zstream = { 0 };
-        if (inflateInit(&zstream) != Z_OK)
+        if (!pkt_size || inflateInit(&zstream) != Z_OK)
             return -1;
         zstream.next_in  = data;
         zstream.avail_in = isize;
@@ -1742,7 +1742,7 @@ static int matroska_decode_buffer(uint8_t **buf, int *buf_size,
     case MATROSKA_TRACK_ENCODING_COMP_BZLIB:
     {
         bz_stream bzstream = { 0 };
-        if (BZ2_bzDecompressInit(&bzstream, 0, 0) != BZ_OK)
+        if (!pkt_size || BZ2_bzDecompressInit(&bzstream, 0, 0) != BZ_OK)
             return -1;
         bzstream.next_in  = data;
         bzstream.avail_in = isize;