lavf/spdifdec: fix demuxing of AAC in IEC 61937

Return value of avpriv_aac_parse_header() is not checked correctly. Fix
it.
Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/spdifdec.c

@@ -57,7 +57,7 @@ static int spdif_get_offset_and_codec(AVFormatContext *s,
         break;
     case IEC61937_MPEG2_AAC:
         init_get_bits(&gbc, buf, AAC_ADTS_HEADER_SIZE * 8);
-        if (avpriv_aac_parse_header(&gbc, &aac_hdr)) {
+        if (avpriv_aac_parse_header(&gbc, &aac_hdr) < 0) {
             if (s) /* be silent during a probe */
                 av_log(s, AV_LOG_ERROR, "Invalid AAC packet in IEC 61937\n");
             return AVERROR_INVALIDDATA;