Clean up XFA code which causes warnings

xfa/fxfa/app/xfa_ffdocview.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "xfa/fxfa/include/xfa_ffdocview.h"
 
 #include "core/fxcrt/include/fx_ext.h"
 #include "xfa/fxfa/app/xfa_ffbarcode.h"
@@ skipping 867 matching lines @@
 CXFA_WidgetAcc* CXFA_WidgetAccIterator::MoveToFirst() {
   return NULL;
 }
 CXFA_WidgetAcc* CXFA_WidgetAccIterator::MoveToLast() {
   return NULL;
 }
 CXFA_WidgetAcc* CXFA_WidgetAccIterator::MoveToNext() {
   CXFA_Node* pItem = m_pCurWidgetAcc ? m_ContentIterator.MoveToNext()
                                      : m_ContentIterator.GetCurrent();
   while (pItem) {
-    if ((m_pCurWidgetAcc = (CXFA_WidgetAcc*)pItem->GetWidgetData())) {
+    m_pCurWidgetAcc = (CXFA_WidgetAcc*)pItem->GetWidgetData();
+    if (m_pCurWidgetAcc)
       return m_pCurWidgetAcc;
-    }
     pItem = m_ContentIterator.MoveToNext();
   }
   return NULL;
 }
 CXFA_WidgetAcc* CXFA_WidgetAccIterator::MoveToPrevious() {
   return NULL;
 }
 CXFA_WidgetAcc* CXFA_WidgetAccIterator::GetCurrentWidgetAcc() {
   return NULL;
 }
 FX_BOOL CXFA_WidgetAccIterator::SetCurrentWidgetAcc(CXFA_WidgetAcc* hWidget) {
   return FALSE;
 }
 void CXFA_WidgetAccIterator::SkipTree() {
   m_ContentIterator.SkipChildrenAndMoveToNext();
   m_pCurWidgetAcc = NULL;
 }