As reported by datao zhang on the mailing list.
action next_syllable { buffer->merge_clusters (last, p); last = p; }
consonant_syllable = (c.N? (H.z?|z.H))* c.N? A? (H.z? | matra_group*)? syllable_tail %(found_consonant_syllable);
-vowel_syllable = (Ra H)? V N? (z.H.c | ZWJ.c)? matra_group* syllable_tail %(found_vowel_syllable);
+vowel_syllable = (Ra H)? V N? (z?.H.c | ZWJ.c)? matra_group* syllable_tail %(found_vowel_syllable);
standalone_cluster = (Ra H)? NBSP N? (z? H c)? matra_group* syllable_tail %(found_standalone_cluster);
non_indic = X %(found_non_indic);