swift alternative for fontDescriptorWithSymbolicTraits ios 8 bug

I'm trying to create a Swift custom text editor (lite version) and got stuck on iOS 8 fontDescriptorWithSymbolicTraits bug, returning nil. Are there any Swift workarounds?

I've created a small project sample here , you can download and run the following scenario:

1. Select a text
2. Click on "B" button
3. Click on "I" button

The app crashes, fontDescriptorWithSymbolicTraits returns nil :(

private func addOrRemoveTraitWithName(traitName: String, traitValue: UInt32) {
    let range = self.textEditor.selectedRange
    let currentAttributesDict = self.textEditor.textStorage.attributesAtIndex(range.location, effectiveRange: nil)
    let currentFont = currentAttributesDict[NSFontAttributeName]

    let fontDescriptor = currentFont?.fontDescriptor()
    let fontNameAttribute = fontDescriptor?.fontAttributes()[UIFontDescriptorNameAttribute]

    var changedFontDescriptor: UIFontDescriptor?

    if fontNameAttribute?.rangeOfString(traitName).location == NSNotFound {
      let existingTraitsWithNewTrait = UIFontDescriptorSymbolicTraits(rawValue: fontDescriptor!.symbolicTraits.rawValue | traitValue)
      changedFontDescriptor = fontDescriptor?.fontDescriptorWithSymbolicTraits(existingTraitsWithNewTrait)
    } else {

      let existingTraitsWithoutTrait = UIFontDescriptorSymbolicTraits(rawValue: fontDescriptor!.symbolicTraits.rawValue & ~traitValue)
      changedFontDescriptor = fontDescriptor?.fontDescriptorWithSymbolicTraits(existingTraitsWithoutTrait)

    }

    let updatedFont = UIFont(descriptor: changedFontDescriptor!, size: 0.0)

    var dict = [String : AnyObject]()
    dict[NSFontAttributeName] = updatedFont
    self.textEditor.textStorage.beginEditing()
    self.textEditor.textStorage.setAttributes(dict, range: range)
    self.textEditor.textStorage.endEditing()
}

I highly recommend to take a quick look at sample project

What options do I have?

I also seen that on Apple documentation the method that was used by other is missing from the SDK & documentation

What others say about this:

1. Font Descriptor returns nil in iOS 8
2. http://www.openradar.me/19922049