Clean up XFA code which causes warnings

xfa/fxfa/app/xfa_ffnotify.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/app/xfa_ffnotify.h"
 
 #include "xfa/fxfa/app/xfa_ffbarcode.h"
 #include "xfa/fxfa/app/xfa_ffcheckbutton.h"
@@ skipping 38 matching lines @@
 
 void CXFA_FFNotify::OnWidgetListItemAdded(CXFA_WidgetData* pSender,
                                           const FX_WCHAR* pLabel,
                                           const FX_WCHAR* pValue,
                                           int32_t iIndex) {
   CXFA_WidgetAcc* pWidgetAcc = static_cast<CXFA_WidgetAcc*>(pSender);
   if (pWidgetAcc->GetUIType() != XFA_ELEMENT_ChoiceList)
     return;
 
   CXFA_FFWidget* pWidget = nullptr;
-  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget))) {
+  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget)) != nullptr) {
     if (pWidget->IsLoaded()) {
       if (pWidgetAcc->IsListBox()) {
         static_cast<CXFA_FFListBox*>(pWidget)->InsertItem(pLabel, iIndex);
       } else {
         static_cast<CXFA_FFComboBox*>(pWidget)->InsertItem(pLabel, iIndex);
       }
     }
   }
 }
 
 void CXFA_FFNotify::OnWidgetListItemRemoved(CXFA_WidgetData* pSender,
                                             int32_t iIndex) {
   CXFA_WidgetAcc* pWidgetAcc = static_cast<CXFA_WidgetAcc*>(pSender);
   if (pWidgetAcc->GetUIType() != XFA_ELEMENT_ChoiceList)
     return;
 
   CXFA_FFWidget* pWidget = nullptr;
-  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget))) {
+  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget)) != nullptr) {
     if (pWidget->IsLoaded()) {
       if (pWidgetAcc->IsListBox()) {
         static_cast<CXFA_FFListBox*>(pWidget)->DeleteItem(iIndex);
       } else {
         static_cast<CXFA_FFComboBox*>(pWidget)->DeleteItem(iIndex);
       }
     }
   }
 }
 
@@ skipping 265 matching lines @@
 
   if (pDocView->GetLayoutStatus() < XFA_DOCVIEW_LAYOUTSTATUS_End)
     return;
 
   CXFA_WidgetAcc* pWidgetAcc =
       static_cast<CXFA_WidgetAcc*>(pSender->GetWidgetData());
   if (!pWidgetAcc)
     return;
 
   CXFA_FFWidget* pWidget = nullptr;
-  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget))) {
+  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget)) != nullptr) {
     if (pWidget->IsLoaded())
       pWidget->AddInvalidateRect();
   }
 }
 
 void CXFA_FFNotify::OnValueChanged(CXFA_Node* pSender,
                                    XFA_ATTRIBUTE eAttr,
                                    CXFA_Node* pParentNode,
                                    CXFA_Node* pWidgetNode) {
   CXFA_FFDocView* pDocView = m_pDoc->GetDocView();
@@ skipping 41 matching lines @@
         pDocView->AddCalculateWidgetAcc(pWidgetAcc);
         pDocView->AddValidateWidget(pWidgetAcc);
       } else if (pWidgetNode->GetNodeItem(XFA_NODEITEM_Parent)->GetClassID() ==
                  XFA_ELEMENT_ExclGroup) {
         pWidgetAcc->UpdateUIDisplay();
       }
       return;
     }
   }
   CXFA_FFWidget* pWidget = nullptr;
-  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget))) {
+  while ((pWidget = pWidgetAcc->GetNextWidget(pWidget)) != nullptr) {
     if (!pWidget->IsLoaded())
       continue;
 
     if (bUpdateProperty)
       pWidget->UpdateWidgetProperty();
     pWidget->PerformLayout();
     pWidget->AddInvalidateRect();
   }
 }
 
@@ skipping 69 matching lines @@
     return;
 
   CXFA_FFWidget* pWidget = XFA_GetWidgetFromLayoutItem(pSender);
   if (!pWidget)
     return;
 
   pDocView->DeleteLayoutItem(pWidget);
   m_pDoc->GetDocProvider()->WidgetPreRemove(pWidget, pWidget->GetDataAcc());
   pWidget->AddInvalidateRect(nullptr);
 }