mRs-/HexColors — pull request #16 by iOSCowboy (2014-12-14 23:12:10+00:00)
Title: Fixed error that would lead to an exception when receiving an empty string

The case:

```objc
[HXColor colorWithHexString:@""];
```

would raise an exception.

This commit places a 'safe-net' for `nil` or empty strings received as argument.