Fix crash at @implementation with a forward reference as base class.

rdar://11020003

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152596 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/ASTMerge/Inputs/interface2.m b/test/ASTMerge/Inputs/interface2.m
index 3fb43f5..2133bd1 100644
--- a/test/ASTMerge/Inputs/interface2.m
+++ b/test/ASTMerge/Inputs/interface2.m
@@ -69,7 +69,7 @@
 @end
 
 // Forward-declared interface
-@class I12, I10;
+@class I10; @interface I12 @end
 @interface I11
 @end