Strings in toplevel answers can sometimes not be read

[triska]

Trying to find out more about #2593, I came up with:

:- use_module(library(crypto)).
:- use_module(library(lists)).
:- use_module(library(format)).

key([188,107,56,177,106,203,66,97,175,194,38,191,198,229,141,146,229,20,93,69,102,40,4,131,143,174,12,181,194,126,26,104]).
nonce([116,67,227,134,77,158,120,180,212,207,93,91]).


d(L, Es) :-
        length(Ls, L),
        maplist(=(a), Ls),
        key(Ks),
        nonce(IV),
        crypto_data_encrypt(Ls, 'chacha20-poly1305', Ks, IV, Es, [tag(_)]).

Yielding:

?- d(626, Es); false.
   Es = "\n\v\x87\ÌÕ\x9d\×l\x80\#\tÄÏíZ2Ç\xa0\\x95\ ..."
   Es = "\n\v\x87\ÌÕ\x9d\×l\x80\#\tÄÏíZ2Ç\xa0\\x95\\x9f\$¸mnM\x1c\\x86\×0xçi¤s\x9a\mgF¾\x7f\\x93\\x1f\¢ÊmDßJ\x1\\x1e\Ñ\fè\x1\§\x9a\®ÉìÇ_Ó^MôÛx1(?\x80\\">Þ¨\x8a\ü\x8a\\x81\\x1e\\x9e\¸9\x93\M\x95\õ~HÚ\x8f\&¶Ã\'m\x97\1E®ÒãÞ\x15\ò\x90\\bL\x8f\\x8f\¦\nÕëy\"\x14\º¢)1\x99\mJ³7ù*\x83\QQ\x8a\Ý5õÅaHWµù\x9f\%\x87\\x96\àÃôý-çÂ+~³F\x97\\x7f\\x18\\\\x1d\h\x6\\x3\\x13\vx*î^\x9b\\x18\\x9d\Ywv5Ái¸W¶\'\x8e\ûWªÓüü\aV\x89\Q»],#ê1¥ý\x99\\x10\\x19\Èî:lLÖ6æA\x12\\x8d\ñ¼\x1a\£_\x8f\Nî)}N¡ï\x1f\𺱥w\x9c\\x97\t\x87\\x8d\¢\x83\\x91\UÎ\x13\¶\x11\4gñéÿk|kmuèè\x88\Ö\\c¨\'\x9f\(\x12\Ì\x13\qSͤ\x9a\ìUq\xe\wܺ;2à´7\x6\?´î_Ûf£\x81\̵v\x9c\\x80\êAW\x95\ÏçÃùÎ\x11\M§<ßy\"#úsEy\x9c\?\x9b\8\r~\n\b¯ô¼Æ¨¶\x9e\ÎýÓG`ý\x8b\\xa0\JðÀ$Ëxlï´Ç\x9b\x\x5\pÊ\x91\]åéç\x91\KN¡ï}\x1\ð\x15\ĸgÀ$¼B\x9b\öµÍÃ\x1\νs(G®-v\x17\Dxe\x1b\]\x1d\cBr?(èÇÍóíA\x12\þÍ\n\xf\]Ûq+\x7f\#Ni\x82\E¢â\vv\x8a\AJS¤\x1f\?¡\x18\påñMÿ5\tØÞ.P\x8b\9\x88\y\x97\\x17\Ð\x3\í\xa0\B·ü*Xè\x18\õDYû\x1e\´\x18\ôA­¢VXe\x9b\\x14\íSç¤\xe\©ØK;N3[øõ_Hcg6ÙÝhPÏú\x12\\x85\\x95\\x2\2C±\x90\\x9c\Ã7¥©»8\x85\N»¿\x99\øß0.\x8a\Ëùè)û\x91\N[\x84\\x99\\x12\e³¾á\x3\tDÏ\x81\3\x5\°Î\x1d\C\b3?+t\x1\\x99\ýïÕëmåÆàWz\'\x89\Þ\x12\ßIíO\x12\çU·[Ñ¢k\x10\vâ\x87\\x84\\x15\+ìQüh\x98\gÁ4Ç¥Sá\x16\.äù/ùX\x98\V+\x93\0"
;  false.

What is the final \0 supposed to say? It should probably be \0\ or \x0\?

?- X = "\0".
   error(syntax_error(incomplete_reduction),read_term/3:0).
?- X = "\0\".
   X = "\x0\".

This occurs with both master and rebis-dev.