Maruku 0.7.3 crashes on itex example

[sattlerc]

Running maruku -i itex on the input

\begin{c}\label{DoubleNegationMonad}
\end{d}
\begin{proof}
Immediate from \ref{Monads}

raises an exception:

maruku/ext/math/parsing.rb:114:in `block in <top (required)>': undefined method `captures' for nil:NilClass (NoMethodError)

[distler]

But

\begin{c}
\label{DoubleNegationMonad}
\end{d}
\begin{proof}
Immediate from \ref{Monads}

works just fine, as does

\begin{c}\label{DoubleNegationMona}
\end{d}
\begin{proof}
Immediate from \ref{Monads}

Curious.

Trivial to "fix", but I don't quite understand what's triggering the problem in the first place.

[distler]

"Fixed" in 97c0489.