Explicitly comparing optionals with nil due to language changes in beta 5

From the [release notes for Xcode 6 beta 5](http://adcdownload.apple.com//Developer_Tools/xcode_6_beta_5_za4gu6/xcode_6_beta_5__release_notes_.pdf):

> Optionals no longer conform to the BooleanType (formerly LogicValue) protocol, so they 
> may no longer be used in place of boolean expressions (they must be explicitly compared with 
> v != nil). This resolves confusion around Bool? and related types, makes code more 
> explicit about what test is expected, and is more consistent with the rest of the language. 

The swift template has to be changed to explicitly check optional Errors for nil.