Fixed audio/spu language selection when none specified in dvdnav.

(cherry picked from commit aef00257)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/access/dvdnav.c

@@ -859,12 +859,18 @@ static char *DemuxGetLanguageCode( demux_t *p_demux, const char *psz_var )
     char *p;
 
     psz_lang = var_CreateGetString( p_demux, psz_var );
+    if( !psz_lang )
+        return strdup(LANGUAGE_DEFAULT);
+
     /* XXX: we will use only the first value
      * (and ignore other ones in case of a list) */
-    if( ( p = strchr( psz_lang, ',' ) ) ) *p = '\0';
+    if( ( p = strchr( psz_lang, ',' ) ) )
+        *p = '\0';
 
     for( pl = p_languages; pl->psz_iso639_1 != NULL; pl++ )
     {
+        if( *psz_lang == '\0' )
+            continue;
         if( !strcasecmp( pl->psz_eng_name, psz_lang ) ||
             !strcasecmp( pl->psz_native_name, psz_lang ) ||
             !strcasecmp( pl->psz_iso639_1, psz_lang ) ||