Precision too low in bnfisprincipal

[Gareth Ma <grhkm21@gmail.com>]

Hi all. I am trying to use `bnfisprincipal`, but it is somehow failing 
even for very small inputs. Here is an example:

default(realprecision, 2000);

bnf = bnfinit(x^2 + 199, flag=1)bnfisprincipal(bnf, bnf.gen[1] ^ 9)
  *** bnfisprincipal: Warning: precision too low for generators, not given.
%7 = [[1]~, []~]