Add a missing 'else'. Found by grep '} if'

No testcase because this did not affect correctness: a declaration can only be
ClassTemplateDecl or a FunctionTemplateDecl, not both.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@170565 91177308-0d34-0410-b5e6-96231b3b80d8