halfopenvertical script glyph not working

[Daniel E. Moctezuma]

Hello,

I'm trying to use the "halfopenvertical" glyph on a Hi-Hat note when writting 
for Drumset.
"halfopen" works fine, but the vertical version doesn't.

I get an error saying "script direction not yet known" and I'm not sure how to 
solve this.
Any ideas?

The glyph in question is documented here (scripts.halfopenvertical):
http://lilypond.org/doc/v2.18/Documentation/notation/the-feta-font#script-glyphs

Here's some sample code demonstrating the issue:

\version "2.18.2"

#(define mydrums '(
         (hihat         cross #f                 5)
         (openhihat     cross "open"             5)
         (closedhihat   cross "stopped"          5)
         (halfopenhihat cross "halfopenvertical" 5)))

\new DrumStaff <<
  \set DrumStaff.drumStyleTable = #(alist->hash-table mydrums)

  \drummode { hh4 hhc hho hhho }
>>

The output I'm getting is:

$ lilypond -ddelete-intermediate-files -dno-point-and-click halfopenvertical.ly
GNU LilyPond 2.18.2
Processing `halfopenvertical.ly'
Parsing...
Interpreting music...
warning: do not know how to interpret articulation:
warning:  scheme encoding:
"halfopenvertical"Preprocessing graphical objects...
halfopenvertical.ly:13:27: programming error: script direction not yet known
  \drummode { hh4 hhc hho
                            hhho }
halfopenvertical.ly:13:27: continuing, cross fingers
[1]    9533 segmentation fault  lilypond -ddelete-intermediate-files 
-dno-point-and-click halfopenvertical.ly