get_n_chars/3 hangs

[flexoron]

Scryer (for comparsion)
$ scryer-prolog -f
?- use_module(library(charsio)).
?- use_module(library(format)).
?- use_module(library(between)).
?- between(0,3,M),(M<3->N=M;N=4),get_n_chars(user_input,N,C),format("<~s>",[C]),writeq(C),nl,fail.
abcdef
<>[]
<a>[a]
<bc>[b,c]
<def
>[d,e,f,'\n']  % N=4 to get the newline, too
   false.
?- halt.

$ tpl  # v2.63.33
?- use_module(library(charsio)).
?- between(0,3,M),(M<3->N=M;N=4),get_n_chars(user_input,N,C),format("<~s>",[C]),writeq(C),nl,fail.
abcdef
% Hangs
% now ^D 
<abcdef             % unexpected
>[a,b,c,d,e,f,'\n'] % unexpected
% Hangs
% now ^D^D (twice)
false
?-

It happens because it starts with N = 0.

?- get_n_chars(user_input,0,C), length(C,N).
<Return>
   C = "\n", N = 1. % unexpected, parameter requests  0 chars.
?-