Fix crashing in CPDFXFA_Document::GetPage()

fpdfsdk/src/fsdk_mgr.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 <algorithm>
 #include <memory>
 
 #include "fpdfsdk/include/fsdk_mgr.h"
@@ skipping 1100 matching lines @@
     if (!pAnnot)
       continue;
     m_fxAnnotArray.push_back(pAnnot);
     pAnnotHandlerMgr->Annot_OnLoad(pAnnot);
   }
 #endif  // PDF_ENABLE_XFA
 
   SetLock(FALSE);
 }
 
+void CPDFSDK_PageView::ClearFXAnnots() {
+  SetLock(TRUE);
+  if (m_pSDKDoc && GetFocusAnnot())
+    m_pSDKDoc->SetFocusAnnot(nullptr);
+  m_CaptureWidget = nullptr;
+  for (CPDFSDK_Annot* pAnnot : m_fxAnnotArray)
+    m_pSDKDoc->GetEnv()->GetAnnotHandlerMgr()->ReleaseAnnot(pAnnot);
+  m_fxAnnotArray.clear();
+  m_pAnnotList.reset();
+  SetLock(FALSE);
+}
+
 void CPDFSDK_PageView::UpdateRects(CFX_RectArray& rects) {
   for (int i = 0; i < rects.GetSize(); i++) {
     CPDF_Rect rc = rects.GetAt(i);
     CPDFDoc_Environment* pEnv = m_pSDKDoc->GetEnv();
     pEnv->FFI_Invalidate(m_page, rc.left, rc.top, rc.right, rc.bottom);
   }
 }
 
 void CPDFSDK_PageView::UpdateView(CPDFSDK_Annot* pAnnot) {
   CPDF_Rect rcWindow = pAnnot->GetRect();
@@ skipping 29 matching lines @@
   CPDFSDK_Annot* pFocusAnnot = m_pSDKDoc->GetFocusAnnot();
   if (!pFocusAnnot)
     return nullptr;
 
   for (CPDFSDK_Annot* pAnnot : m_fxAnnotArray) {
     if (pAnnot == pFocusAnnot)
       return pAnnot;
   }
   return nullptr;
 }