Fix use of dyn_cast.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57927 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 8c63060..7a3c6bd 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -2406,7 +2406,7 @@
     // &X[4] and &4[X] refers to X if X is not a pointer.
   
     NamedDecl *D = getPrimaryDecl(cast<ArraySubscriptExpr>(E)->getBase());
-    ValueDecl *VD = dyn_cast<ValueDecl>(D);
+    ValueDecl *VD = dyn_cast_or_null<ValueDecl>(D);
     if (!VD || VD->getType()->isPointerType())
       return 0;
     else