Fix for a crash in NativeViewAccessibilityWin

ui/views/accessibility/native_view_accessibility_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/accessibility/native_view_accessibility_win.h"
 
 #include <oleacc.h>
 #include <UIAutomationClient.h>
 
 #include <set>
@@ skipping 511 matching lines @@
     }
   }
 
   if (!child_view) {
     // No child found.
     *disp_child = NULL;
     return E_FAIL;
   }
 
   *disp_child = child_view->GetNativeViewAccessible();
-  (*disp_child)->AddRef();
-  return S_OK;
+  if (*disp_child) {
+    (*disp_child)->AddRef();
+    return S_OK;
+  }
+
+  return E_FAIL;
 }
 
 STDMETHODIMP NativeViewAccessibilityWin::get_accChildCount(LONG* child_count) {
   if (!child_count)
     return E_INVALIDARG;
 
   if (!view_ || !view_->GetWidget())
     return E_FAIL;
 
   *child_count = view_->child_count();
@@ skipping 983 matching lines @@
     if (view == NULL || view == view_) {
       alert_target_view_storage_ids_.erase(
           alert_target_view_storage_ids_.begin() + i);
     } else {
       ++i;
     }
   }
 }
 
 }  // namespace views