demux: mp4: fix heap buffer ofw with zero chunk (fix #12356)

(cherry picked from commit 929970aecfc91725ba243953ccb5197fa797c0a8)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/demux/mp4/mp4.c

@@ -2118,7 +2118,7 @@ static void TrackGetESSampleRate( demux_t *p_demux,
         return;
     }
 
-    if( p_track->i_chunk_count <= 0 )
+    if( p_track->i_chunk_count == 0 )
         return;
 
     /* */
@@ -2158,7 +2158,7 @@ static int TrackCreateES( demux_t *p_demux, mp4_track_t *p_track,
     demux_sys_t *p_sys = p_demux->p_sys;
     unsigned int i_sample_description_index;
 
-    if( p_sys->b_fragmented )
+    if( p_sys->b_fragmented || p_track->i_chunk_count == 0 )
         i_sample_description_index = 1; /* XXX */
     else
         i_sample_description_index =