[FIX] Check that the CFBundleDisplayName is not nil

With Xcode 6, when you create a new project the `CFBundleDisplayName` is not filled by default, so when you use the `GCDWebUploader` class it crashes because of a value of the array is nil

To fix that I just check whether the `CFBundleDisplayName` is present and if not I uses the `CFBundleName`