MLP packetizer: avoid SIGFPE with samplerate of 0

(cherry picked from commit ad1bc94879755bc7bf10638ef9e8b2d2ff895a44)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/packetizer/mlp.c

@@ -294,10 +294,13 @@ static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
                 msg_Info( p_dec, "MLP channels: %d samplerate: %d",
                           p_sys->mlp.i_channels, p_sys->mlp.i_rate );
 
+                if( p_sys->mlp.i_rate > 0 )
+                {
                     const mtime_t i_end_date = date_Get( &p_sys->end_date );
                     date_Init( &p_sys->end_date, p_sys->mlp.i_rate, 1 );
                     date_Set( &p_sys->end_date, i_end_date );
                 }
+            }
 
             p_dec->fmt_out.audio.i_rate     = p_sys->mlp.i_rate;
             p_dec->fmt_out.audio.i_channels = p_sys->mlp.i_channels;