dts_header: initialize SUBSTREAM_LBR size to 0

It's a substream and can't work alone, so a size of 0 is legitimate.

Fixes #28773 (Use of uninitialised value)

(cherry picked from commit b23f09b258)
Signed-off-by: Thomas Guillem <thomas@gllm.fr>

modules/packetizer/dts_header.c

@@ -342,6 +342,7 @@ static int dts_header_ParseLBRExtSubstream( vlc_dts_header_t *p_header,
     bs_skip( &s, 16 );
     uint16_t nLBRScaledBitRate_LSW = bs_read( &s, 16 );
     p_header->i_bitrate = nLBRScaledBitRate_LSW | ((nLBRBitRateMSnybbles & 0xF0) << 12);
+    p_header->i_frame_size = 0;
     return VLC_SUCCESS;
 }