Cannot romanize string including uncombined hangul characters (e.g. ㅏㄹ)

[osori]

KeyError                                  Traceback (most recent call last)
<ipython-input-9-a36b3cd68e86> in <module>
      1 r = Romanizer("ㅏㄹ")
----> 2 r.romanize()

<ipython-input-1-afb14c96da98> in romanize(self)
    290                 s = Syllable(char)
    291                 #try:
--> 292                 _romanized += onset[s.initial] + vowel[s.medial] + coda[s.final]
    293                 #except Exception as e:
    294                 #    _romanized += "[에러:" + str(e) + "]"

KeyError: 12623