Don't call the demux close function ourselves, the core will do it.

modules/misc/lua/demux.c

@@ -256,7 +256,6 @@ static int Demux( demux_t *p_demux )
     {
         msg_Warn( p_demux, "Error while runing script %s, "
                   "function parse() not found", psz_filename );
-        Close_LuaPlaylist( VLC_OBJECT( p_demux ) );
         return VLC_EGENERIC;
     }
 
@@ -265,7 +264,6 @@ static int Demux( demux_t *p_demux )
         msg_Warn( p_demux, "Error while runing script %s, "
                   "function parse(): %s", psz_filename,
                   lua_tostring( L, lua_gettop( L ) ) );
-        Close_LuaPlaylist( VLC_OBJECT( p_demux ) );
         return VLC_EGENERIC;
     }