Not work for JSON format

[xndcn]

When input file is raw JSON format, it produces error:

/usr/local/lib/node_modules/jison/lib/cli.js:142
var settings = grammar.options || {};
^
TypeError: Cannot read property 'options' of undefined
at Object.generateParserString (/usr/local/lib/node_modules/jison/lib/cli.js:142:27)
at processGrammar (/usr/local/lib/node_modules/jison/lib/cli.js:74:22)
at processInputFile (/usr/local/lib/node_modules/jison/lib/cli.js:106:22)
at Object.cliMain as main
at Object. (/usr/local/lib/node_modules/jison/lib/cli.js:185:9)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)

[lambdabaa]

I think this was a regression introduced after 0.4.13