[libclang] Fix crash on invalid code. Fixes rdar://10451854

llvm-svn: 144766
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 0b9c37a..64b931f 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -853,6 +853,9 @@
   }
 
   void handleTopLevelDecl(Decl *D) {
+    if (!D)
+      return;
+
     // FIXME: Currently ObjC method declarations are incorrectly being
     // reported as top-level declarations, even though their DeclContext
     // is the containing ObjC @interface/@implementation.  This is a