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

[iv-mexx]

From the release notes for Xcode 6 beta 5:

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.

[rentzsch]

Thanks!