Exception for some invalid timezones

[MartinMajor]

tz = require("timezone/loaded");

date = "2015-12-14 14:30";

console.log(tz(date, "Europe/Berlin")); // correct timezone => correct result
console.log(tz(date, "Germany/Berlin")); // invalid timezone => returned UTC
console.log(tz(date, "Berlin")); // invalid timezone => returned UTC
console.log(tz(date, "Germany")); // invalid timezone => throws exception

TypeError: Cannot read property 'rules' of undefined
    at find (/test/node_modules/timezone/index.js:45:14)
    at convertToPOSIX (/test/node_modules/timezone/index.js:76:29)
    at Object.convert (/test/node_modules/timezone/index.js:180:23)
    at /test/node_modules/timezone/index.js:209:41
    at Object.<anonymous> (/test/example.js:8:13)
    at Module._compile (module.js:434:26)
    at Object.Module._extensions..js (module.js:452:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Function.Module.runMain (module.js:475:10)

For some incorrect timezones UTC time is returned, for some exception is thrown. I'm not sure what is desired behaviour (I would prefer stricter validation) but it should be definitely consistent. And the exception should said something more descriptive than Cannot read property 'rules' of undefined.