avformat/matroskadec: remove now duplicate doctype check

See: b8d7f318
See: d9fe6b92Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/matroskadec.c

@@ -2088,8 +2088,7 @@ static int matroska_read_header(AVFormatContext *s)
     if (ebml.version         > EBML_VERSION      ||
         ebml.max_size        > sizeof(uint64_t)  ||
         ebml.id_length       > sizeof(uint32_t)  ||
-        ebml.doctype_version > 3                 ||
-        !ebml.doctype) {
+        ebml.doctype_version > 3) {
         av_log(matroska->ctx, AV_LOG_ERROR,
                "EBML header using unsupported features\n"
                "(EBML version %"PRIu64", doctype %s, doc version %"PRIu64")\n",