fix a bug on to_binary/1:

2> uuid:to_binary(uuid:v4()).
** exception error: no function clause matching lists:'-filter/2-lc$^0/1-0-'(<<148,5,248,17,164,141,76,236,146,74,68,108,101,149,252,
                                                                               229>>) (lists.erl, line 1271)
     in function  uuid:to_binary/1 (uuid.erl, line 54)