make-ngram-pfsg cannot handle 1-grams?

[Matthias Thomae]

Hello,

I am using version 1.3.1 and would like to generate a unigram lm in pfsg
format. I encounter problems when calling make-ngram-pfsg, see example
below. Any ideas?

Regards.
Matthias

-------------------------------------------------------------------------

  > cat test.txt
rote kugel
gruene kugel

  > ngram-count -text test.txt -lm test.lm -order 1
warning: discount coeff 1 is out of range: -0
tho at odin: ~/worktho/nadia/lm > cat test.lm

\data\
ngram 1=5

\1-grams:
-0.4929155      </s>
-99     <s>
-0.748188       gruene
-0.4929155      kugel
-0.748188       rote

\end\

 > make-ngram-pfsg test.lm
output_for_node: got empty name
<s> tag undefined in LM