Fix warnings introduced by r165826.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@165829 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index a00f60f..4161078 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1739,6 +1739,8 @@
     case attr::AcquiredBefore:
     case attr::AcquiredAfter:
       return false;
+    default:
+      ;
   }
 
   const OwnershipAttr *OA = dyn_cast<OwnershipAttr>(A);