Fix a crashier in CPDFSDK_Document::GetPageView()

fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp

Index: fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
diff --git a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
index d37038d2af6ef580edbcfacb16bf9671a50a7385..7c2bbf0aea34414cdd757b3ccc1310b3a3965c29 100644
--- a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
+++ b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
@@ -45,28 +45,26 @@ CPDFXFA_Document::CPDFXFA_Document(CPDF_Document* pPDFDoc,
 }
 
 CPDFXFA_Document::~CPDFXFA_Document() {
-  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
-    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
-
-  delete m_pSDKDoc;
-
-  if (m_pPDFDoc) {
-    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
-    if (pParser)
-      delete pParser;
-    else
-      delete m_pPDFDoc;
-  }
   if (m_pXFADoc) {
     IXFA_App* pApp = m_pApp->GetXFAApp();
     if (pApp) {
       IXFA_DocHandler* pDocHandler = pApp->GetDocHandler();
-      if (pDocHandler) {
+      if (pDocHandler)
         CloseXFADoc(pDocHandler);
-      }
     }
     delete m_pXFADoc;
+    m_pXFADoc = nullptr;
   }
+  if (m_pPDFDoc) {
+    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
+    if (pParser)
+      delete pParser;
+    else
+      delete m_pPDFDoc;
+  }
+  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
+    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
+  delete m_pSDKDoc;
 }
 
 FX_BOOL CPDFXFA_Document::LoadXFADoc() {
@@ -487,7 +485,6 @@ void CPDFXFA_Document::PageViewEvent(IXFA_PageView* pPageView,
   if (!pPage)
     return;
   pPage->SetXFAPageView(nullptr);
-  m_pSDKDoc->GetPageView(pPage)->ClearFXAnnots();

[jun_fang, 2016/02/01 09:54:29]

When a XFA page is deleted, it doesn't need to clear annotations on this page.
That's because a XFA page is dynamically created by layout process. 
A XFA page is a virtual and dynamic page. Annotations will be mapped to a new
XFA page during performing layout. 

 }
 
 void CPDFXFA_Document::WidgetEvent(IXFA_Widget* hWidget,