tools::parseLatex() crashes on "\\verb{}"

Dear r-devel,

I've tried tools::parseLatex() to parse some documentation files, it works
generally well but it  it has some issues when "\\verb{}" is used.

```
tools::parseLatex("\\code{hello}")
# \code{hello}
tools::parseLatex("\\anything{hello}")
# \anything{hello}
tools::parseLatex("\\verb{hello}")
# crashes the session
```

Thanks,

Antoine