Emit a warning when the body of an if block is a NullStmt.

llvm-svn: 42840
diff --git a/clang/test/Sema/default.c b/clang/test/Sema/default.c
index b51ab9a..92f7278 100644
--- a/clang/test/Sema/default.c
+++ b/clang/test/Sema/default.c
@@ -3,6 +3,6 @@
 void f5 (int z) { 
   if (z) 
     default:  // expected-error {{not in switch statement}}
-      ; 
+      ; // expected-warning {{if statement has empty body}}
 }