[NTG-context] unicode subscripts

Hi! Unicode subscripts do not work (at least, in math): \starttext $a₀₁₂₃₄₅₆₇₈₉₋₌₊$ \stoptext prints only "a". The file char-def.lua contains block like this: [0x2080]={ category="no", description="SUBSCRIPT ZERO", direction="en", linebreak="al", specials={ "sub", 0x0030 }, unicodeslot=0x2080, }, Which file should handle this "specials={ "sub", 0x0030 }"? P.S.: Superscript digits work. Probably, the font contains ¹ but not ₁.