latm: Always reconfigure if no extradata was set previously

AAC LOAS can have new audio config objects in the stream itself.

Make sure the decoder reconfigures itself when the first one arrives
midstream.

Bug-Id: 644
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/aacdec.c

@@ -3030,7 +3030,8 @@ static int latm_decode_audio_specific_config(struct LATMContext *latmctx,
     if (bits_consumed < 0)
         return AVERROR_INVALIDDATA;
 
-    if (ac->oc[1].m4ac.sample_rate != m4ac.sample_rate ||
+    if (!latmctx->initialized ||
+        ac->oc[1].m4ac.sample_rate != m4ac.sample_rate ||
         ac->oc[1].m4ac.chan_config != m4ac.chan_config) {
 
         av_log(avctx, AV_LOG_INFO, "audio config changed\n");