texmath-0.12.5: test/writer/tex/msub-02.test

<<< native
[ ESub
    (EGrouped [ EPhantom (EIdentifier "fail") , EIdentifier "X" ])
    (ENumber "0")
, ESymbol Rel "="
, ESub (EIdentifier "X") (ENumber "0")
]
>>> tex
{\phantom{fail}X}_{0} = X_{0}