Problem if not git config exists

I do not have .gitconfig file and this generator fails when trying to format the username

/usr/lib/node_modules/slush-express-api/slushfile.js:22
var username = string.toLowerCase();
^
TypeError: Cannot read property 'toLowerCase' of undefined
at format (/usr/lib/node_modules/slush-express-api/slushfile.js:22:26)
at /usr/lib/node_modules/slush-express-api/slushfile.js:60:19
at Object. (/usr/lib/node_modules/slush-express-api/slushfile.js:63:3)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Module.require (module.js:365:17)
at require (module.js:384:17)
at Liftoff.handleArguments (/usr/lib/node_modules/slush/bin/slush.js:90:3)