demux: avi: fix non fixed sample size ADTS/AAC (fix #12727)

(cherry picked from commit 600d5e3974ef4ee7242dbc3411dd0dfe59f029c1)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/avi/avi.c

@@ -445,6 +445,11 @@ static int Open( vlc_object_t * p_this )
                     tk->i_blocksize = 0; /* fix vorbis VBR decoding */
                 }
 
+                if ( tk->i_codec == VLC_CODEC_MP4A )
+                {
+                    tk->i_samplesize = 0; /* ADTS/AAC VBR */
+                }
+
                 es_format_Init( &fmt, AUDIO_ES, tk->i_codec );
 
                 fmt.audio.i_channels        = p_auds->p_wf->nChannels;