Cannot read property 'toLowerCase' of undefined

[smic]

I installed localize-mainmenu via npm, but following error when executing:

/usr/local/lib/node_modules/localize-mainmenu/localizor.js:49
var targetLang = child.attr["target-language"].toLowerCase();
^

TypeError: Cannot read property 'toLowerCase' of undefined
at /usr/local/lib/node_modules/localize-mainmenu/localizor.js:49:51
at XmlDocument.XmlElement.eachChild (/usr/local/lib/node_modules/localize-mainmenu/node_modules/xmldoc/lib/xmldoc.js:63:18)
at /usr/local/lib/node_modules/localize-mainmenu/localizor.js:41:12
at tryToString (fs.js:414:3)
at FSReqWrap.readFileAfterClose [as oncomplete] (fs.js:401:12)